General strategy for using Newton's second law to solve problems:
|
|
- Ophelia Foster
- 5 years ago
- Views:
Transcription
1 Chapter 4B: Applications of Newton's Laws Tuesday, September 17, :00 PM General strategy for using Newton's second law to solve problems: 1. Draw a diagram; select a coördinate system 2. Identify relevant objects/agents 3. Sketch an interaction scheme 4. Draw a free-body diagram, using the coördinate system chosen in Step 1 5. Apply Newton's second law to each relevant object, in each direction specified by the coördinate system chosen in Step 1 Example: Static equilibrium Determine the tension in the string. Solution: Ch4BPreliminary Page 1
2 Example: Static equilibrium Calculate the tension in the strings if (assume the strings have no mass) a. the labelled angles are both 30 b. the labelled angles are both 10 c. one labelled angle is 40 and the other labelled angle is 60 Ch4BPreliminary Page 2
3 Ch4BPreliminary Page 3
4 Mass and Weight Ch4BPreliminary Page 4
5 Apparently we don't "feel" gravitational forces directly; what we do feel is contact forces. This explains why we feel weightless when falling, and why astronauts feel weightless when they are in orbit around the Earth (in "free fall"). When you stand on your bathroom scale, you "feel" the normal force exerted by the scale on you; this is what the scale also measures. You feel a similar normal force when you sit on a chair. If you are just standing on your bathroom scale, the normal force from the scale balances your weight (i.e., the gravitational force that the Earth exerts on you), which is why the scale reading (which measures this normal force) equals your weight. Make sure you understand the difference between mass and weight; your mass is a measure of the substances that you consist of, and is independent of your location. Your weight is a measure of the gravitational force that the Earth exerts on you; although it's proportional to your mass, it is not the same as your mass (W = mg). If you were on the Moon, your weight would be different, because what you feel as your weight would be the normal force that the surface of the Moon exerts on you, which is equal to the gravitational force that the Moon exerts on you. When you are accelerating, your apparent weight (i.e., the normal force exerted on you by the surface you're standing on) depends on your acceleration. Example: Apparent weight Calculate the apparent weight of a 70 kg person in an elevator that is a. accelerating upward at 4 m/s 2. b. moving upward at a constant speed of 5 m/s. c. accelerating downward at 2 m/s 2. Ch4BPreliminary Page 5
6 Thus, if the cable snaps, then the normal force becomes zero, which means the apparent weight of the passenger becomes zero; the passenger feels weightless. Friction You may have noticed that it is difficult to push a refrigerator. The reason for this is that the bottom of the refrigerator is rough, and so is the floor. You may also have noticed that it's more difficult to move the refrigerator over a carpet than over a smooth floor, because the carpet is rougher than the floor. Thus, the frictional force between two surfaces depends on the surfaces. This dependence is so complicated that we don't have any good theory for predicting the friction between two surfaces; the best we can do is just measure the frictional forces in experiments. Further reflection will reveal other facts about friction. You may have noticed that when you begin to push on the refrigerator, it doesn't move. However, as you gradually increase your pushing force, eventually the refrigerator will Ch4BPreliminary Page 6
7 move. Once the refrigerator is moving, it takes less pushing force to keep it moving than the force needed to get it moving in the first place. Conclusion: the coefficient of static friction is greater than the coefficient of kinetic friction. Furthermore, if you stack another heavy object on the refrigerator, it will be harder to move it. Similarly, if someone presses down on the refrigerator, that also makes it harder to move. Thus, frictional forces depend on the normal force acting between the two surfaces in contact. Conclusions: f s µ s n f k = µ k n Typically, the coefficient of kinetic friction is less than the coefficient of static friction for the same pair of surfaces; the coefficient of rolling friction is much less than the coefficient of static friction for the same surfaces. µ r << µ k < µ s Sample coefficients of friction are found on Page 144 of your textbook. For example, for rubber on concrete, approximate typical values are µ s = 1.00, µ k = 0.80, µ r = 0.02 Example: A refrigerator of mass 100 kg is resting on a horizontal floor. The coefficients of friction between the refrigerator and the floor are µ s = 1.00 and µ k = Determine a. the force needed to get the refrigerator moving. b. the force needed to keep the refrigerator moving at a constant speed once it has already started moving. Ch4BPreliminary Page 7
8 Ch4BPreliminary Page 8
9 In the previous problem, what happens if the original 980 N applied force is maintained once the refrigerator is moving? That is, the kinetic friction force opposing the motion is 715 N, but the applied force is greater than the frictional force, so the net horizontal force on the refrigerator is = 265 N. Thus, the refrigerator accelerates to the right. Air drag very complicated, much like friction; we don't have good theories of air drag, so we can't predict very well the amount of air drag that will be present in some situation; the best we can do is to experiment, sometimes with scale models (wind tunnels, for example, are used for experimentation) As an approximation, that is reasonably good in certain circumstances, the force of air drag (i.e., air resistance) in newtons is about: D = 0.3Av 2 where A is the cross-sectional area of the object that is moving through the air (in square metres), and the speed is measured in m/s. Notice the quadratic dependence on speed; this means if the speed doubles, the air drag quadruples. This makes it very difficult indeed to get things moving through the air at high speeds. A lot of engineering design work goes into reducing air drag by designing shapes and using materials for objects that will reduce the coefficient "0.3" to a smaller number. A more detailed formula is Ch4BPreliminary Page 9
10 D = 0.25ρAv 2 where ρ represents the density of air; a typical value for the density of air at sea level is ρ = 1.22 kg/m 3. Remember that these formulas are very rough approximations, and experts in various fields will have their own better approximations that deal specifically with their own situations. A consequence of air drag is terminal speed. If you drop an object from rest, the gravitational force on the object is approximately constant for the entire fall, but the air drag starts off very small (because the speed is small) and then increases rapidly with increasing speed. At some point, if the object falls for long enough, the air drag will grow so large that it balances the gravitational force. After this point, the net force acting on the falling object will be zero, so the object's speed will be constant; this is called the object's terminal speed. Example: Terminal speed 1. Calculate the terminal speed of a human being of mass 70 kg. 2. Calculate the area of a parachute needed to reduce the terminal speed of a human being of mass 70 kg to (i) 10 km/h, and (ii) 5 km/h. Assume that the person falls feet-first, so that we can estimate his or her cross section as approximately 0.1 m 2. (We can probably stand on a 1-foot square kitchen tile without "sticking out", right?) Thus, the drag force on the person is about When the drag force is equal to the force of gravity on the person, then the net force on the person is zero, and the person's speed is constant. Thus, the terminal speed satisfies Ch4BPreliminary Page 10
11 This is very fast. You can minimize the terminal speed by increasing the crosssectional area, which increases the drag force. One way to do this is to fall "belly-flop" style instead of feet-first. Another way is to use a parachute, which is explored in Part (b). Remember that such calculations are only approximate. The actual drag force depends on many factors that are not included in the formula, such as the shape of the object, the material on the surface of the object, and so on. Ch4BPreliminary Page 11
12 Do the results seem reasonable? Not really, because typical sky-diving parachutes have cross-sectional areas in the range of 10 m 2 to 50 m 2. Evidently, sky divers hit the ground at speeds significantly greater than what we assumed. Suppose we take a typical parachute cross-sectional area of 50 m 2. Here is the resulting terminal speed: This seems awfully fast. Would you want to be hitting the ground at this speed? We can compare this terminal speed with speeds attained by jumping from various heights. Or, better yet, let's use the kinematics equations to determine the height from which you would have to drop a ball so that it hits the ground at a speed of 6.8 m/s (assuming no air resistance): Ch4BPreliminary Page 12
13 This seems reasonable, as the height is less than the height of a typical one-storey roof. I've seen athletic teenagers jump off one-storey roofs with no ill effects (I'd probably break my legs), so jumping from a lesser height is probably safe. It's reasonable to expect a parachute to slow a novice sky-diver to similar speeds. Blocks and pulleys Example: Calculate the acceleration of the system and the magnitudes of the inter-block forces if a. a 10 N force acts on the left-most block towards the right. b. a 10 N force acts on the right-most block towards the left. Assume there is no friction between the blocks and the surface they rest on. Ch4BPreliminary Page 13
14 Ch4BPreliminary Page 14
15 Ch4BPreliminary Page 15
16 Ch4BPreliminary Page 16
17 Example: Calculate the tension in each string and the acceleration of each block. Assume that the strings are massless and don't stretch, and that the pulley is massless and there is no friction at the bearing. Further assume that the string slides on the pulley without friction (or, more accurately, turns the pulley without slipping, so that friction need not be considered). Ch4BPreliminary Page 17
18 Ch4BPreliminary Page 18
19 Ch4BPreliminary Page 19
20 Example: Calculate the tension in the string and the acceleration of each block. Assume that the strings are massless and don't stretch, and that the pulley is massless and there is no friction at the bearing. Further assume that the string slides on the pulley without friction (or turns the pulley without friction needing to be considered). Suppose that the coefficient of static friction between the 2 kg block and the horizontal surface is 0.8, and that the coefficient of kinetic friction between the same surfaces is 0.5. Ch4BPreliminary Page 20
21 Now for an important bit of strategy: Note that if the tension force is less than the maximum value of the static friction force, then the blocks will not move. The static friction force will adjust itself to match the applied force, up to a point; if the applied force exceeds the maximum static friction force, then the blocks move, and then kinetic friction will apply. Thus, let's first assume that the blocks do not move, and we'll calculate the tension force. Then we'll compare the tension force to the maximum force of static friction. If the tension force is greater than the maximum static friction force, then we know the Ch4BPreliminary Page 21
22 blocks will move, and we'll re-solve a part of the problem using the kinetic friction force to determine the actual accelerations of the blocks. Here goes the first step, using static friction: The tension force is greater than the maximum static friction force, so the blocks actually move. Thus, we can go back to equation (*) and replace f by the force of kinetic friction to determine the actual tension in the string. Ch4BPreliminary Page 22
23 Example: Calculate the tension in the string and the acceleration of each block. Assume that the strings are massless and don't stretch, and that the pulley is massless and there is no friction at the bearing. Further assume that the string slides on the pulley without friction (or turns the pulley without friction needing to be considered). (a) Suppose that the surface is frictionless. (b) Suppose that the coefficient of static friction between the 2 kg block and the slanted surface is 0.8, and that the coefficient of kinetic friction between the same surfaces is 0.5. Ch4BPreliminary Page 23
24 (a) If the surface is frictionless, then f = 0, and the equations above simplify to (also noting that the sine of 30 degrees is 1/2): Because we are only interested in calculating the tension in the string and the acceleration, we can ignore equation (1). Solve equation (2) for T and substitute the result in equation (3), to obtain: Ch4BPreliminary Page 24
25 Substituting the value of the acceleration into equation (2), we can solve for the tension in the string: (b) Now for an important bit of strategy: Note that if the tension force is less than the maximum value of the static friction force, then the blocks will not move. The static friction force will adjust itself to match the applied force, up to a point; if the applied force exceeds the maximum static friction force, then the blocks move, and then kinetic friction will apply. Thus, let's first assume that the blocks do not move, and we'll calculate the tension force. Then we'll compare the tension force to the maximum force of static friction. If the tension force is greater than the maximum static friction force, then we know the blocks will move, and we'll re-solve a part of the problem using the kinetic friction force to determine the actual accelerations of the blocks. Here goes the first step, using static friction: Ch4BPreliminary Page 25
26 The tension force is greater than the maximum static friction force, so the blocks actually move. Thus, we can go back to equation (*) and replace f by the force of kinetic friction to determine the actual tension in the string. Note that the acceleration is less in this problem than in the previous problem, which is not surprising, since (because of the slope of the slanted surface) gravity works against the acceleration of the 2-kg block. Finally, notice that in all of the problems in this chapter, time has been ignored. This is Ch4BPreliminary Page 26
27 the usual tactic in first-year physics: We simplify as much as possible at the beginning, sometimes at the cost of oversimplification. As an example of a situation where time must be included in the analysis, consider the following massive block suspended by a thread, and having another thread attached below it: Suppose that you pull down on the bottom thread; what happens? Well, it depends on how gradually you increase the force as you pull down. If you give the bottom thread a sudden jerk, then the bottom thread will snap. If you give the bottom thread a slow, gradual increase in force, then the top thread will snap. You can explain this for yourself if you draw free-body diagrams for each thread (that's right, the threads, not the block), and notice that the tension in the top thread is greater, because it also has to support the weight of the block. However, if you give the lower thread a sudden jerk, there is not enough time for the force to be transmitted to the upper thread, and so the lower thread will break. It's a bit like a train engine pulling on a long train of cars; not every car begins moving at once. Instead, the first car begins moving, and there is a slight time delay until the coupling between the first car and the second car engages, which gets the second car moving. Then, after another short time delay, the third car begins moving, and so on. You can see the same phenomenon (for a different reason) when a line of cars gets moving when the traffic light changes from red to green; there is a time delay for each car in the line to get moving. You can experience this phenomenon (with the block and threads) in every day life when you break a paper towel from its roll, or break toilet paper from its roll. If you "snap" the paper, then it will break along one of the perforations, but if you pull steadily the paper will unroll without breaking off. The same thing happens at the grocery store when you break off a plastic bag from its roll in the produce department. A sudden snap breaks a bag from the roll, but a gradual pull just unrolls the bags. There are other practical consequences to the tension experienced by different members of hanging structures. Consider the following hanging walkway. Ch4BPreliminary Page 27
28 Moral: Critical thinking involves actively searching for errors. It's unreasonable to expect that no errors will be made; however, one needs systematic searches for errors. This is one of the great strengths of science: Nothing is taken for granted, and nothing is taken by authority. Each idea is always tested, over and over again. The upside is that errors are found and corrected; the system of science is "self-correcting." The downside is that new ideas are often subject to vicious attacks, and sensitive people are often turned away from scientific research because of its rough-and-tumble nature. Even the very greats suffer the slings and arrows of attack (to be fair, this is common in every field of creative endeavour, not just science), and sometimes they succumb; witness Boltzmann's suicide, which may have been driven by the vicious attacks on his revolutionary ideas in statistical mechanics. Resilience is helpful in all fields of endeavour, so perhaps it's not surprising that it is helpful for survival in scientific research too. Ch4BPreliminary Page 28
Chapter 5: Applications of Newton's laws Tuesday, September 17, :00 PM. General strategy for using Newton's second law to solve problems:
Ch5 Page 1 Chapter 5: Applications of Newton's laws Tuesday, September 17, 2013 10:00 PM General strategy for using Newton's second law to solve problems: 1. Draw a diagram; select a coördinate system
More informationGeneral strategy for using Newton's second law to solve problems:
Chapter 4B: Applications of Newton's Laws Tuesday, September 17, 2013 10:00 PM General strategy for using Newton's second law to solve problems: 1. Draw a diagram; select a coördinate system 2. Identify
More informationGeneral strategy for using Newton's second law to solve problems:
Chapter 4B: Applications of Newton's Laws Tuesday, September 17, 2013 10:00 PM General strategy for using Newton's second law to solve problems: 1. Draw a diagram; select a coördinate system 2. Identify
More informationChapter 4. Forces and Newton s Laws of Motion. continued
Chapter 4 Forces and Newton s Laws of Motion continued Quiz 3 4.7 The Gravitational Force Newton s Law of Universal Gravitation Every particle in the universe exerts an attractive force on every other
More informationHSC PHYSICS ONLINE B F BA. repulsion between two negatively charged objects. attraction between a negative charge and a positive charge
HSC PHYSICS ONLINE DYNAMICS TYPES O ORCES Electrostatic force (force mediated by a field - long range: action at a distance) the attractive or repulsion between two stationary charged objects. AB A B BA
More informationChapter 7 Newton s Third Law
Chapter 7 Newton s Third Law Chapter Goal: To use Newton s third law to understand interacting objects. Slide 7-2 Chapter 7 Preview Slide 7-3 Chapter 7 Preview Slide 7-4 Chapter 7 Preview Slide 7-6 Chapter
More informationChapter 4 Force and Motion
Chapter 4 Force and Motion Units of Chapter 4 The Concepts of Force and Net Force Inertia and Newton s First Law of Motion Newton s Second Law of Motion Newton s Third Law of Motion More on Newton s Laws:
More information3 Using Newton s Laws
3 Using Newton s Laws What You ll Learn how Newton's first law explains what happens in a car crash how Newton's second law explains the effects of air resistance 4(A), 4(C), 4(D), 4(E) Before You Read
More informationWebreview practice test. Forces (again)
Please do not write on test. ID A Webreview 4.3 - practice test. Forces (again) Multiple Choice Identify the choice that best completes the statement or answers the question. 1. A 5.0-kg mass is suspended
More informationDynamic equilibrium: object moves with constant velocity in a straight line. = 0, a x = i
Dynamic equilibrium: object moves with constant velocity in a straight line. We note that F net a s are both vector quantities, so in terms of their components, (F net ) x = i (F i ) x = 0, a x = i (a
More informationSection /07/2013. PHY131H1F University of Toronto Class 12 Preclass Video by Jason Harlow. Based on Knight 3 rd edition Ch. 7, pgs.
PHY131H1F University of Toronto Class 12 Preclass Video by Jason Harlow Section 7.1 Based on Knight 3 rd edition Ch. 7, pgs. 167-184 When a hammer hits a nail, it exerts a forward force on the nail At
More informationForces and Newton s Laws
chapter 3 Forces and Newton s Laws section 3 Using Newton s Laws Before You Read Imagine riding on a sled, or in a wagon, or perhaps a school bus that stops quickly or suddenly. What happens to your body
More informationUnit 2 Part 2: Forces Note 1: Newton`s Universal Law of Gravitation. Newton`s Law of Universal Gravitation states: Gravity. Where: G = M = r =
Unit 2 Part 2: Forces Note 1: Newton`s Universal Law of Gravitation Gravity Newton`s Law of Universal Gravitation states: Where: G = = M = m = r = Ex 1: What is the force of gravity exerted on a 70.0 kg
More informationReading Quiz. Chapter 5. Physics 111, Concordia College
Reading Quiz Chapter 5 1. The coefficient of static friction is A. smaller than the coefficient of kinetic friction. B. equal to the coefficient of kinetic friction. C. larger than the coefficient of kinetic
More informationChapter 6 Dynamics I: Motion Along a Line
Chapter 6 Dynamics I: Motion Along a Line Chapter Goal: To learn how to solve linear force-and-motion problems. Slide 6-2 Chapter 6 Preview Slide 6-3 Chapter 6 Preview Slide 6-4 Chapter 6 Preview Slide
More information= 40 N. Q = 60 O m s,k
Sample Exam #2 Technical Physics Multiple Choice ( 6 Points Each ): F app = 40 N 20 kg Q = 60 O = 0 1. A 20 kg box is pulled along a frictionless floor with an applied force of 40 N. The applied force
More informationIsaac Newton ( ) 1687 Published Principia Invented Calculus 3 Laws of Motion Universal Law of Gravity
Isaac Newton (1642-1727) 1687 Published Principia Invented Calculus 3 Laws of Motion Universal Law of Gravity Newton s First Law (Law of Inertia) An object will remain at rest or in a constant state of
More informationForces and Motion in One Dimension
Nicholas J. Giordano www.cengage.com/physics/giordano Forces and Motion in One Dimension Applications of Newton s Laws We will learn how Newton s Laws apply in various situations We will begin with motion
More informationThursday February 8. Write these equations in your notes if they re not already there. You will want them for Exam 1 & the Final.
Assignment 4 due Friday like almost every Friday Pre-class due 15min before class like every class Help Room: Here, 6-9pm Wed/Thurs SI: Morton 222, M&W 7:15-8:45pm Office Hours: 204 EAL, 10-11am Wed or
More informationIntroductory Physics PHYS101
Introductory Physics PHYS101 Dr Richard H. Cyburt Office Hours Assistant Professor of Physics My office: 402c in the Science Building My phone: (304) 384-6006 My email: rcyburt@concord.edu TRF 9:30-11:00am
More informationWelcome back to Physics 211
Welcome back to Physics 211 Today s agenda: Weight Friction Tension 07-1 1 Current assignments Thursday prelecture assignment. HW#7 due this Friday at 5 pm. 07-1 2 Summary To solve problems in mechanics,
More informationPHYSICS 231 Laws of motion PHY 231
PHYSICS 231 Laws of motion 1 Newton s Laws First Law: If the net force exerted on an object is zero the object continues in its original state of motion; if it was at rest, it remains at rest. If it was
More informationPS113 Chapter 4 Forces and Newton s laws of motion
PS113 Chapter 4 Forces and Newton s laws of motion 1 The concepts of force and mass A force is described as the push or pull between two objects There are two kinds of forces 1. Contact forces where two
More informationEnd-of-Chapter Exercises
End-of-Chapter Exercises For all these exercises, assume that all strings are massless and all pulleys are both massless and frictionless. We will improve our model and learn how to account for the mass
More informationPhysics B Newton s Laws AP Review Packet
Force A force is a push or pull on an object. Forces cause an object to accelerate To speed up To slow down To change direction Unit: Newton (SI system) Newton s First Law The Law of Inertia. A body in
More informationChapter 4. Forces and Newton s Laws of Motion. continued
Chapter 4 Forces and Newton s Laws of Motion continued 4.9 Static and Kinetic Frictional Forces When an object is in contact with a surface forces can act on the objects. The component of this force acting
More informationPHYSICS. Chapter 7 Lecture FOR SCIENTISTS AND ENGINEERS A STRATEGIC APPROACH 4/E RANDALL D. KNIGHT Pearson Education, Inc.
PHYSICS FOR SCIENTISTS AND ENGINEERS A STRATEGIC APPROACH 4/E Chapter 7 Lecture RANDALL D. KNIGHT Chapter 7 Newton s Third Law IN THIS CHAPTER, you will use Newton s third law to understand how objects
More informationWeb practice Chapter 4 Newton's Laws of Motion
Name: Class: _ Date: _ Web practice Chapter 4 Newton's Laws of Motion Multiple Choice Identify the choice that best completes the statement or answers the question. 1. If we know an object is moving at
More informationChapter 4. The Laws of Motion
Chapter 4 The Laws of Motion Classical Mechanics Describes the relationship between the motion of objects in our everyday world and the forces acting on them Conditions when Classical Mechanics does not
More informationDynamics: Forces and Newton s Laws of Motion
Lecture 7 Chapter 5 Physics I Dynamics: Forces and Newton s Laws of Motion Course website: http://faculty.uml.edu/andriy_danylov/teaching/physicsi Today we are going to discuss: Chapter 5: Force, Mass:
More informationWS-CH-4 Motion and Force Show all your work and equations used. Isaac Newton ( )
AP PHYSICS 1 WS-CH-4 Motion and Force Show all your work and equations used. Isaac Newton (1643-1727) Isaac Newton was the greatest English mathematician of his generation. He laid the foundation for differential
More informationLab #5: Newton s First Law
Lab #5: Newton s First Law Reading Assignment: Chapter 5 Chapter 6, Sections 6-1 through 6-3, Section 6-5 Introduction: A common misnomer is that astronauts experience zero g s during space flight. In
More informationThe Laws of Motion. Newton s first law Force Mass Newton s second law Gravitational Force Newton s third law Examples
The Laws of Motion Newton s first law Force Mass Newton s second law Gravitational Force Newton s third law Examples Gravitational Force Gravitational force is a vector Expressed by Newton s Law of Universal
More informationForces & Newton s Laws FR Practice Problems
1) A drag-racing car speeds up from rest to 22 m/s in 2 s. The car has mass 800 kg; the driver has mass 80 kg. a) Calculate the acceleration of the car. b) Calculate the net force on the car. c) Which
More informationPhysics for Scientists and Engineers. Chapter 6 Dynamics I: Motion Along a Line
Physics for Scientists and Engineers Chapter 6 Dynamics I: Motion Along a Line Spring, 008 Ho Jung Paik Applications of Newton s Law Objects can be modeled as particles Masses of strings or ropes are negligible
More informationThe Laws of Motion. Gravity and Friction
The Laws of Motion Gravity and Friction Types of Forces Think about all the things you pushed or pulled today. You might have pushed toothpaste out of a tube. Maybe you pulled out a chair to sit down.
More informationPYP 001 FIRST MAJOR EXAM CODE: TERM: 151 SATURDAY, OCTOBER 17, 2015 PAGE: 1
TERM: 151 SATURDAY, OCTOBER 17, 2015 PAGE: 1 *Read the following (20) questions and choose the right answer: 1 The figure below represents the speed-time graph for the motion of a vehicle during a 7.0-minute
More informationDynamics (Newton s Laws) - The Causes of Motion
AP Physics-B Dynamics (Newton s Laws) - The Causes of Motion Introduction: This unit introduces the most basic of all scientific concepts, the interaction between forces and matter. You should understand
More informationBEFORE YOU READ. Forces and Motion Gravity and Motion STUDY TIP. After you read this section, you should be able to answer these questions:
CHAPTER 2 1 SECTION Forces and Motion Gravity and Motion BEFORE YOU READ After you read this section, you should be able to answer these questions: How does gravity affect objects? How does air resistance
More informationCHAPTER 4 TEST REVIEW -- Answer Key
AP PHYSICS Name: Period: Date: DEVIL PHYSICS BADDEST CLASS ON CAMPUS 50 Multiple Choice 45 Single Response 5 Multi-Response Free Response 3 Short Free Response 2 Long Free Response AP EXAM CHAPTER TEST
More informationChapter 6. Force and Motion II
Chapter 6 Force and Motion II 6 Force and Motion II 2 Announcement: Sample Answer Key 3 4 6-2 Friction Force Question: If the friction were absent, what would happen? Answer: You could not stop without
More informationI. What are forces? A. Characteristics:
Chapter 5: forces I. What are forces? A. Characteristics: 1. Forces result from the interaction of objects. A FORCE is a push or a pull that one object exerts on another. 2. How are forces measured: a.
More informationCh 6 Using Newton s Laws. Applications to mass, weight, friction, air resistance, and periodic motion
Ch 6 Using Newton s Laws Applications to mass, weight, friction, air resistance, and periodic motion Newton s 2 nd Law Applied Galileo hypothesized that all objects gain speed at the same rate (have the
More informationReview: Advanced Applications of Newton's Laws
Review: Advanced Applications of Newton's Laws 1. The free-body diagram of a wagon being pulled along a horizontal surface is best represented by a. A d. D b. B e. E c. C 2. The free-body diagram of a
More informationPH201 Chapter 5 Solutions
PH201 Chapter 5 Solutions 5.4. Set Up: For each object use coordinates where +y is upward. Each object has Call the objects 1 and 2, with and Solve: (a) The free-body diagrams for each object are shown
More informationNewton s Laws. A force is simply a push or a pull. Forces are vectors; they have both size and direction.
Newton s Laws Newton s first law: An object will stay at rest or in a state of uniform motion with constant velocity, in a straight line, unless acted upon by an external force. In other words, the bodies
More informationQ2. A book whose mass is 2 kg rests on a table. Find the magnitude of the force exerted by the table on the book.
AP Physics 1- Dynamics Practice Problems FACT: Inertia is the tendency of an object to resist a change in state of motion. A change in state of motion means a change in an object s velocity, therefore
More informationy(t) = y 0 t! 1 2 gt 2. With y(t final ) = 0, we can solve this for v 0 : v 0 A ĵ. With A! ĵ =!2 and A! = (2) 2 + (!
1. The angle between the vector! A = 3î! 2 ĵ! 5 ˆk and the positive y axis, in degrees, is closest to: A) 19 B) 71 C) 90 D) 109 E) 161 The dot product between the vector! A = 3î! 2 ĵ! 5 ˆk and the unit
More informationDynamics; Newton s Laws of Motion
Dynamics; Newton s Laws of Motion Force A force is any kind of push or pull on an object. An object at rest needs a force to get it moving; a moving object needs a force to change its velocity. The magnitude
More informationMASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Physics 8.01 Physics Fall Term = # v x. t " =0. are the values at t = 0.
MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Physics 8.01 Physics Fall Term 2012 Exam 1: Practice Problems! d r!! d v! One-Dimensional Kinematics: v =, a = dt dt t " =t v x (t)! v x,0 = # a x (
More informationAP Physics C: Mechanics Practice (Newton s Laws including friction, resistive forces, and centripetal force).
AP Physics C: Mechanics Practice (Newton s Laws including friction, resistive forces, and centripetal force). 1981M1. A block of mass m, acted on by a force of magnitude F directed horizontally to the
More informationLecture 5. Dynamics. Forces: Newton s First and Second
Lecture 5 Dynamics. Forces: Newton s First and Second What is a force? It s a pull or a push: F F Force is a quantitative description of the interaction between two physical bodies that causes them to
More informationFriction Can Be Rough
10.1 Observe and Find a Pattern Friction Can Be Rough Observe the following experiment: Rest a brick on a rough surface. Tie a string around the brick and attach a large spring scale to it. Pull the scale
More informationKinematics. v (m/s) ii. Plot the velocity as a function of time on the following graph.
Kinematics 1993B1 (modified) A student stands in an elevator and records his acceleration as a function of time. The data are shown in the graph above. At time t = 0, the elevator is at displacement x
More informationLecture Presentation Chapter 5 Applying Newton s Laws
Lecture Presentation Chapter 5 Applying Newton s Laws Suggested Videos for Chapter 5 Prelecture Videos Static and Dynamic Equilibrium Weight and Apparent Weight Friction Video Tutor Solutions Applying
More information4 Study Guide. Forces in One Dimension Vocabulary Review
Date Period Name CHAPTER 4 Study Guide Forces in One Dimension Vocabulary Review Write the term that correctly completes the statement. Use each term once. agent force Newton s second law apparent weight
More informationForce mediated by a field - long range: action at a distance: The attractive or repulsion between two stationary charged objects.
VISUAL PHYSICS ONLINE DYNAMICS TYPES O ORCES 1 Electrostatic force orce mediated by a field - long range: action at a distance: The attractive or repulsion between two stationary charged objects. AB A
More informationGeneral Physics I Spring Applying Newton s Laws
General Physics I Spring 2011 Applying Newton s Laws 1 Equilibrium An object is in equilibrium if the net force acting on it is zero. According to Newton s first law, such an object will remain at rest
More informationWelcome to Forces an anticipation guide A force is defined as a push or a pull When answering the following true or false statements, offer a
Welcome to Forces an anticipation guide A force is defined as a push or a pull When answering the following true or false statements, offer a real-life example that justifies your answer. You haven t answered
More informationPhysics 2211 ABC Quiz #3 Solutions Spring 2017
Physics 2211 ABC Quiz #3 Solutions Spring 2017 I. (16 points) A block of mass m b is suspended vertically on a ideal cord that then passes through a frictionless hole and is attached to a sphere of mass
More informationChapter 5 Force and Motion
Chapter 5 Force and Motion Chapter Goal: To establish a connection between force and motion. Slide 5-2 Chapter 5 Preview Slide 5-3 Chapter 5 Preview Slide 5-4 Chapter 5 Preview Slide 5-5 Chapter 5 Preview
More informationCircle the correct answer. For those questions involving calculations, working MUST be shown to receive credit.
Dynamics Assignment 3 Name: Multiple Choice. Circle the correct answer. For those questions involving calculations, working MUST be shown to receive credit. 1. Which statement is always true regarding
More informationGeneral Physics I Spring Applying Newton s Laws
General Physics I Spring 2011 pplying Newton s Laws 1 Friction When you push horizontally on a heavy box at rest on a horizontal floor with a steadily increasing force, the box will remain at rest initially,
More informationChapter 4. Dynamics: Newton s Laws of Motion. That is, describing why objects move
Chapter 4 Dynamics: Newton s Laws of Motion That is, describing why objects move orces Newton s 1 st Law Newton s 2 nd Law Newton s 3 rd Law Examples of orces: Weight, Normal orce, Tension, riction ree-body
More informationPhysics 101 Lecture 5 Newton`s Laws
Physics 101 Lecture 5 Newton`s Laws Dr. Ali ÖVGÜN EMU Physics Department The Laws of Motion q Newton s first law q Force q Mass q Newton s second law q Newton s third law qfrictional forces q Examples
More informationPHYSICS. Chapter 5 Lecture FOR SCIENTISTS AND ENGINEERS A STRATEGIC APPROACH 4/E RANDALL D. KNIGHT Pearson Education, Inc.
PHYSICS FOR SCIENTISTS AND ENGINEERS A STRATEGIC APPROACH 4/E Chapter 5 Lecture RANDALL D. KNIGHT Chapter 5 Force and Motion IN THIS CHAPTER, you will learn about the connection between force and motion.
More informationFree-Body Diagrams: Introduction
Free-Body Diagrams: Introduction Learning Goal: To learn to draw free-body diagrams for various real-life situations. Imagine that you are given a description of a real-life situation and are asked to
More informationDynamics Multiple Choice Homework
Dynamics Multiple Choice Homework PSI Physics Name 1. In the absence of a net force, a moving object will A. slow down and eventually stop B. stop immediately C. turn right D. move with constant velocity
More informationPHYSICS. Chapter 5 Lecture FOR SCIENTISTS AND ENGINEERS A STRATEGIC APPROACH 4/E RANDALL D. KNIGHT Pearson Education, Inc.
PHYSICS FOR SCIENTISTS AND ENGINEERS A STRATEGIC APPROACH 4/E Chapter 5 Lecture RANDALL D. KNIGHT Chapter 5 Force and Motion IN THIS CHAPTER, you will learn about the connection between force and motion.
More informationLecture PowerPoints. Chapter 5 Physics for Scientists & Engineers, with Modern Physics, 4 th edition. Giancoli
Lecture PowerPoints Chapter 5 Physics for Scientists & Engineers, with Modern Physics, 4 th edition 2009 Pearson Education, Inc. This work is protected by United States copyright laws and is provided solely
More informationPHYSICS - CLUTCH CH 04: INTRO TO FORCES (DYNAMICS)
!! www.clutchprep.com FORCE, APPLIED FORCE, TENSION A force is either a push or a pull. Unit = ( ) - We ll represent all forces as a We ll refer to generic forces as forces. - Usually on an object by a
More informationThe Concept of Force Newton s First Law and Inertial Frames Mass Newton s Second Law The Gravitational Force and Weight Newton s Third Law Analysis
The Laws of Motion The Concept of Force Newton s First Law and Inertial Frames Mass Newton s Second Law The Gravitational Force and Weight Newton s Third Law Analysis Models using Newton s Second Law Forces
More informationPhysics 2A Chapter 4: Forces and Newton s Laws of Motion
Physics 2A Chapter 4: Forces and Newton s Laws of Motion There is nothing either good or bad, but thinking makes it so. William Shakespeare It s not what happens to you that determines how far you will
More informationApex Grammar School O & A Level Evening Classes. Physics EVALUATION TEST PAPER. REAL EXAMINATION QUESTIONS for Secondary 4
Apex Grammar School O & A Level Evening Classes O Level Power Revision Series EVALUATION TEST PAPER REAL EXAMINATION QUESTIONS for Secondary 4 Name: Time Start: Date: Time End: Total Marks : / 40 40 questions
More informationDynamics: Forces and Newton s Laws of Motion
Lecture 7 Chapter 5 Dynamics: Forces and Newton s Laws of Motion Course website: http://faculty.uml.edu/andriy_danylov/teaching/physicsi Today we are going to discuss: Chapter 5: Force, Mass: Section 5.1
More informationWhat is a Force? Free-Body diagrams. Contact vs. At-a-Distance 11/28/2016. Forces and Newton s Laws of Motion
Forces and Newton s Laws of Motion What is a Force? In generic terms: a force is a push or a pull exerted on an object that could cause one of the following to occur: A linear acceleration of the object
More information2. If a net horizontal force of 175 N is applied to a bike whose mass is 43 kg what acceleration is produced?
Chapter Problems Newton s 2nd Law: Class Work 1. A 0.40 kg toy car moves at constant acceleration of 2.3 m/s 2. Determine the net applied force that is responsible for that acceleration. 2. If a net horizontal
More informationAP Physics 1 - Test 05 - Force and Motion
P Physics 1 - Test 05 - Force and Motion Score: 1. brick slides on a horizontal surface. Which of the following will increase the magnitude of the frictional force on it? Putting a second brick on top
More informationPHYS 101 Previous Exam Problems. Force & Motion I
PHYS 101 Previous Exam Problems CHAPTER 5 Force & Motion I Newton s Laws Vertical motion Horizontal motion Mixed forces Contact forces Inclines General problems 1. A 5.0-kg block is lowered with a downward
More informationLecture Presentation Chapter 5 Applying Newton s Laws
Lecture Presentation Chapter 5 Applying Newton s Laws Suggested Videos for Chapter 5 Prelecture Videos Static and Dynamic Equilibrium Weight and Apparent Weight Friction Video Tutor Solutions Applying
More informationAn Accelerating Hockey Puck
Example 5.1 An Accelerating Hockey Puck A hockey puck having a mass of 0.30 kg slides on the frictionless, horizontal surface of an ice rink. Two hockey sticks strike the puck simultaneously, exerting
More informationPhysics 201 Lecture 16
Physics 01 Lecture 16 Agenda: l Review for exam Lecture 16 Newton s Laws Three blocks are connected on the table as shown. The table has a coefficient of kinetic friction of 0.350, the masses are m 1 =
More informationSolved Problems. 3.3 The object in Fig. 3-1(a) weighs 50 N and is supported by a cord. Find the tension in the cord.
30 NEWTON'S LAWS [CHAP. 3 Solved Problems 3.1 Find the weight on Earth of a body whose mass is (a) 3.00 kg, (b) 200 g. The general relation between mass m and weight F W is F W ˆ mg. In this relation,
More informationBIT1002 Newton's Laws. By the end of this you should understand
BIT1002 Newton's Laws By the end of this you should understand Galileo's Law of inertia/newton's First Law What is an Inertial Frame The Connection between force and Acceleration: F=ma 4. The Third Law
More informationUNIT XX: DYNAMICS AND NEWTON S LAWS. DYNAMICS is the branch of mechanics concerned with the forces that cause motions of bodies
I. Definition of FORCE UNIT XX: DYNAMICS AND NEWTON S LAWS DYNAMICS is the branch of mechanics concerned with the forces that cause motions of bodies FORCE is a quantitative interaction between two (or
More informationCHAPTER 4 NEWTON S LAWS OF MOTION
62 CHAPTER 4 NEWTON S LAWS O MOTION CHAPTER 4 NEWTON S LAWS O MOTION 63 Up to now we have described the motion of particles using quantities like displacement, velocity and acceleration. These quantities
More informationForces and Newton s Laws Notes
Forces and Newton s Laws Notes Force An action exerted on an object which can change the motion of the object. The SI unit for force is the Newton (N) o N = (kg m)/s 2 o Pound is also a measure of force
More informationPHY131 Summer 2011 Class 5 Notes
PHY131 Summer 2011 Class 5 Notes 5/31/11 PHY131H1F Summer Class 5 Today: Equilibrium Mass, Weight, Gravity Friction, Drag Rolling without slipping Examples of Newton s Second Law Pre-class Reading Quiz.
More information3/10/2019. What Is a Force? What Is a Force? Tactics: Drawing Force Vectors
What Is a Force? A force acts on an object. A force requires an agent, something that acts on the object. If you throw a ball, your hand is the agent or cause of the force exerted on the ball. A force
More informationApplying Newton s Laws
Applying Newton s Laws Free Body Diagrams Draw and label the forces acting on the object. Examples of forces: weight, normal force, air resistance, friction, applied forces (like a push or pull) Velocity
More informationCHAPTER 2. FORCE and Motion. CHAPTER s Objectives
19 CHAPTER 2 FORCE and Motion CHAPTER s Objectives To define a force To understand the relation between force and motion In chapter 1, we understood that the Greek philosopher Aristotle was the first who
More informationChapter 5: Applications of Newton s Laws. Brent Royuk Phys-111 Concordia University
Chapter 5: Applications of Newton s Laws Brent Royuk Phys-111 Concordia University Friction Definition: a that opposes motion Three types Static Contact Kinetic Sliding Rolling Friction depends on two
More informationChapter 5: Applications of Newton s Laws
Chapter 5: Applications of Newton s Laws Brent Royuk Phys-111 Concordia University Friction Definition: a that opposes motion Three types Static Contact Kinetic Sliding Rolling Friction depends on two
More informationLecture 6. Applying Newton s Laws Free body diagrams Friction
Lecture 6 Applying Newton s Laws Free body diagrams Friction ACT: Bowling on the Moon An astronaut on Earth kicks a bowling ball horizontally and hurts his foot. A year later, the same astronaut kicks
More informationPhys 1401: General Physics I
1. (0 Points) What course is this? a. PHYS 1401 b. PHYS 1402 c. PHYS 2425 d. PHYS 2426 2. (0 Points) Which exam is this? a. Exam 1 b. Exam 2 c. Final Exam 3. (0 Points) What version of the exam is this?
More information7.1 Interacting Systems p Action/reaction pairs p Newton s Third Law p Ropes and Pulleys p.
7.1 Interacting Systems p. 183-185 7.2 Action/reaction pairs p. 185-189 7.3 Newton s Third Law p. 189-194 7.4 Ropes and Pulleys p. 194-198 7.5 Interacting-system Problems p. 198-202 1 7.1 Interacting Systems
More informationChapter 4. Forces in One Dimension
Chapter 4 Forces in One Dimension Chapter 4 Forces in One Dimension In this chapter you will: *VD Note Use Newton s laws to solve problems. Determine the magnitude and direction of the net force that causes
More informationfor any object. Note that we use letter, m g, meaning gravitational
Lecture 4. orces, Newton's Second Law Last time we have started our discussion of Newtonian Mechanics and formulated Newton s laws. Today we shall closely look at the statement of the second law and consider
More informationKinematics and Dynamics
AP PHYS 1 Test Review Kinematics and Dynamics Name: Other Useful Site: http://www.aplusphysics.com/ap1/ap1- supp.html 2015-16 AP Physics: Kinematics Study Guide The study guide will help you review all
More information1 In the absence of a net force, a moving object will. slow down and eventually stop stop immediately turn right move with constant velocity turn left
Slide 1 / 51 1 In the absence of a net force, a moving object will slow down and eventually stop stop immediately turn right move with constant velocity turn left Slide 2 / 51 2 When a cat sleeps on a
More information