Or why this won t work very well

Size: px
Start display at page:

Download "Or why this won t work very well"

Transcription

1 Friction

2 Friction Friction causes objects to slow down. Friction creates heat. Friction degrades an object s energy

3 Friction is: Friction: A force that resists the relative motion or tendency to such motion of two bodies in contact. Source: Dictionary.com Or why this won t work very well

4 Places where friction is good The soles of shoes Car tires The feet of table legs Rock climbing holds Brakes etc

5 Places where friction is bad In engines In transmissions On the bottoms of skis and snowboards (To a point) When you are trying to move a box by pushing it along the floor etc

6 What causes friction?

7 Source of Friction At the microscopic level even the smoothest of surfaces is dotted with little mountain peaks. The tips of the peaks are the only parts that touch the other material. Only a very small portion of the apparent surface area is in contact with the other surface Picture of extremely smooth mica with a scanned probe microscope This causes extremely high pressures to form on the parts that touch. This causes the two surfaces to become welded almost at the points of contact

8 Friction Surface imperfections and micro-welds.

9 Source of friction (continued) The true surface contact area is proportional to the normal force because the peaks will deform plastically when force is applied increasing the contact area Plastic deformation: to change shape permanently without fracturing Other lesser reasons for friction Surface adhesion between pure metals Ploughing of one surface by the other harder one Elastic deformation

10 Experiment: Does the friction force depend on surface area? We stick a 1kg mass on a piece of plexiglass on top of the clean surface and, using a Newton meter, pull the weight across the table with the string provided at constant speed. We put the same weight on a different piece of plexiglass with drastically different surface area and repeat What do you notice?

11 Friction doesn t depend on apparent surface area (much) You may have noticed a small dependence. This is partially due to the greater weight of the larger piece of plexiglass, and also partially due to the fact that there is a dependence of friction on surface area, just one that is small enough to be ignored under most circumstances. Why is the friction force approximately independent of surface area? Because as discussed previously the materials plastically deform at the peaks depending on the pressure increasing real surface area. RSA = real surface area, F = Normal Force, SA = Surface area, F/SA = P Pressure, C = constant depending on the materials RSA = SA x P x C = SA x F/SA x C = F x C

12 Static Friction

13 Static Friction Normal force Friction, Resistance Applied Force Objects at rest. Applied force is insufficient to move object. Weight = mg

14 Finally something useful.. The only formula you need for friction forces: Friction Force = coefficient of kinetic friction x norrnal force or F f = µf n

15 Newton s Second and Third Laws Newton s Second Law: If there is an unbalanced force on an object it will accelerate according to F Unbalanced = m a Newton s Third Law: If you exert a force on an object it exerts an equal and opposite force on you

16 Block at Rest on a Table

17 Normal Force From Newton s third law we know that if gravity or some other force pushes an object (like a block) into a second object (like a table) that second object will be exerting an equal force back on the first. Normal force is the force the table exerts back on the block Normal force is always exerted perpendicular to the surface Friction Force is always parallel to the surface So if the table is horizontal and gravity is the only force on the block F n = -F g

18 Normal force on a hill Normal force is exerted perpendicular to the surface in accordance with Newton s Third law No unbalanced force so the block is stationary or at least not accelerating

19 Static Friction The relationship is µ s = force of friction/normal force. Where µ is called the coefficient of static friction. It has no units and varies between 0 and 2 in general. We usually rearrange the equation: f = µ s N (Mu)

20 Example of Static Friction What is the coefficient of static friction between a tabletop and a 2 kg block of wood if a 2 N force is required to start the block moving? Identify knowns and unknown: m = 2 kg, applied force = 2 N, v = 0, µ s =?

21 Appropriate equation: f = µ N. What is N? On a level surface the normal force upward is equal to the weight of the object downward, i.e. N = W = mg. So, f = µ mg or µ = f/mg = 2 N/(2 kg *9.8m/s 2 ) µ = 0.102

22 Kinetic Friction

23 Kinetic Friction The word kinetic stems from the Greek word, kinema meaning motion, so kinetic friction deals with the friction present when motion is occurring. The resistance is less because the microscopic impediments are being sheared off and no time for micro-welds to form.

24 Kinetic Friction Constant Less than static friction. This is the key to non-skid brakes. Force Frictional Applied Force, N

25 Why? The slightly larger value for static friction results from irregularities and contaminants on the surfaces and is less accurate in general than the coefficient of kinetic friction Between (very) carefully cleaned surfaces the difference between the two coefficients disappears

26 Compare skidding with no skidding. A car moving at 25 m/s slams on its brakes. The coefficient of static friction with the road is 1.2 and the kinetic coefficient is How far does the car slide? Knowns: v o = 25 m/s, v = 0 m/s, µ s = 0.4. Unknown: x =? Equations: v 2 =v o2 +2 ax, F = ma, N = mg, f =µn.

27 Solve for x: x = -v o2 /2a = -v o2 /2(-F/m) =-v o2 /2(-µN/m) =-v o2 /2(-µmg/m) = v 2 o2 /2 /2µg =(25 m/s) 2 /(2*0.85*9.8 m/s 2 ) =37.5 m

28 Now, solve the same problem using non-skid brakes so the wheels keep turning while the car slows down. In this case we use the state coefficient of friction x = v o2 /2µg =(25 m/s) 2 /(2*1.2*9.8 m/s 2 ) =26.6m Imagine if the pavement wear wet and the coefficient of kinetic friction was The stopping distance would be nearly 75 m!

29 Frictional force and normal force. Frictional force is proportional to the normal force, f α N. On a level surface N = W, but what if someone is lifting up on the object? Won t that reduce the normal force?

30 Free Body Diagram N + T = W, so N = W T. If T pulls at some angle, then just decompose into components. Normal, N Lift from person,t Weight, W

31 Example: A person pulls on a 300 N crate with a rope that makes a 37 0 angle to the ground. If the coefficient of static friction is 0.6, how much tension must the person exert to get the crate moving? Knowns: W = 300 N, θ = 37 o, µ = 0.6. Unknown: T =? Equations: f = µn. All forces balance when at rest.

32 Horizontal Tension = T cos θ Vertical Tension = T sin θ Net vertical force = N + Tsin θ W = 0, so N = W - Tsin θ. Net horizontal force = Tcos θ f = 0 Tcos θ = f = µn = µ(w - Tsin θ), so

33 Tcos θ = µ(w - Tsin θ) Tcos θ + µ Tsin θ = µw T(cos θ + µ sin θ) = µw T = µw/(cos θ + µ sin θ) T = 0.6*300N/(cos *sin30 0 ) T = 180N/( ) T = 180 N/(1.166) T = 154 N

+F N = -F g. F g = m٠a g

+F N = -F g. F g = m٠a g Force Normal = F N Force Normal (or the Normal Force, abbreviated F N ) = F N = The contact force exerted by a surface on an object. The word Normal means perpendicular to Therefore, the Normal Force is

More information

There are two main types of friction:

There are two main types of friction: Section 4.15: Friction Friction is needed to move. Without friction, a car would sit in one spot spinning its tires, and a person would not be able to step forward. However, the motion of an object along

More information

Physics 8 Wednesday, October 19, Troublesome questions for HW4 (5 or more people got 0 or 1 points on them): 1, 14, 15, 16, 17, 18, 19. Yikes!

Physics 8 Wednesday, October 19, Troublesome questions for HW4 (5 or more people got 0 or 1 points on them): 1, 14, 15, 16, 17, 18, 19. Yikes! Physics 8 Wednesday, October 19, 2011 Troublesome questions for HW4 (5 or more people got 0 or 1 points on them): 1, 14, 15, 16, 17, 18, 19. Yikes! Troublesome HW4 questions 1. Two objects of inertias

More information

Topic: Force PHYSICS 231

Topic: Force PHYSICS 231 Topic: Force PHYSICS 231 Current Assignments Homework Set 2 due this Thursday, Jan 27, 11 pm Reading for next week: Chapters 10.1-6,10.10,8.3 2/1/11 Physics 231 Spring 2011 2 Key Concepts: Force Free body

More information

Forces and Newton s Laws Notes

Forces 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 information

Chapter 4. Forces and Newton s Laws of Motion. continued

Chapter 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 information

WS-CH-4 Motion and Force Show all your work and equations used. Isaac Newton ( )

WS-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 information

Consider the case of a 100 N. mass on a horizontal surface as shown below:

Consider the case of a 100 N. mass on a horizontal surface as shown below: 1.9.1 Introduction The study of friction is called: The force of friction is defined as: The force of friction acting between two surfaces has three properties: i) ii) iii) Consider the case of a 100 N.

More information

Physics B Newton s Laws AP Review Packet

Physics 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 information

2. A 10 kg box is being pushed by a 100 N force 30 above the horizontal. The acceleration of the box is 5 m/s 2. What is the value of µ k?

2. A 10 kg box is being pushed by a 100 N force 30 above the horizontal. The acceleration of the box is 5 m/s 2. What is the value of µ k? Physics Whiteboard Forces with Friction 1. A 70 kg block is being pushed across a tabletop with a constant force of 350 N exerted in the direction of travel. If the coefficient of kinetic friction (µ k

More information

HSC PHYSICS ONLINE B F BA. repulsion between two negatively charged objects. attraction between a negative charge and a positive charge

HSC 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 information

Q2. A book whose mass is 2 kg rests on a table. Find the magnitude of the force exerted by the table on the book.

Q2. 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 information

Friction Can Be Rough

Friction Can Be Rough 8.1 Observe and Find a Pattern Friction Can Be Rough Perform 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 information

Chapter 4 Force and Motion

Chapter 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 information

Newton s Laws Student Success Sheets (SSS)

Newton s Laws Student Success Sheets (SSS) --- Newton s Laws unit student success sheets--- Page 1 Newton s Laws Student Success Sheets (SSS) HS-PS2-1 HS-PS2-2 NGSS Civic Memorial High School - Physics Concept # What we will be learning Mandatory

More information

Figure 5.1a, b IDENTIFY: Apply to the car. EXECUTE: gives.. EVALUATE: The force required is less than the weight of the car by the factor.

Figure 5.1a, b IDENTIFY: Apply to the car. EXECUTE: gives.. EVALUATE: The force required is less than the weight of the car by the factor. 51 IDENTIFY: for each object Apply to each weight and to the pulley SET UP: Take upward The pulley has negligible mass Let be the tension in the rope and let be the tension in the chain EXECUTE: (a) The

More information

FORCE. Definition: Combining Forces (Resultant Force)

FORCE. Definition: Combining Forces (Resultant Force) 1 FORCE Definition: A force is either push or pull. A Force is a vector quantity that means it has magnitude and direction. Force is measured in a unit called Newtons (N). Some examples of forces are:

More information

2. Kinetic friction - The force that acts against an object s motion. - Occurs once static friction has been overcome and object is moving

2. Kinetic friction - The force that acts against an object s motion. - Occurs once static friction has been overcome and object is moving Section 2.14: Friction Friction is needed to move. Without friction, a car would sit in one spot spinning its tires, and a person would not be able to step forward. However, the motion of an object along

More information

Applying Newton s Laws

Applying 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 information

d. Determine the power output of the boy required to sustain this velocity.

d. Determine the power output of the boy required to sustain this velocity. AP Physics C Dynamics Free Response Problems 1. A 45 kg boy stands on 30 kg platform suspended by a rope passing over a stationary pulley that is free to rotate. The other end of the rope is held by the

More information

POGIL: Newton s First Law of Motion and Statics. Part 1: Net Force Model: Read the following carefully and study the diagrams that follow.

POGIL: Newton s First Law of Motion and Statics. Part 1: Net Force Model: Read the following carefully and study the diagrams that follow. POGIL: Newton s First Law of Motion and Statics Name Purpose: To become familiar with the forces acting on an object at rest Part 1: Net Force Model: Read the following carefully and study the diagrams

More information

Chapter 5 Lecture. Pearson Physics. Newton's Laws of Motion. Prepared by Chris Chiaverina Pearson Education, Inc.

Chapter 5 Lecture. Pearson Physics. Newton's Laws of Motion. Prepared by Chris Chiaverina Pearson Education, Inc. Chapter 5 Lecture Pearson Physics Newton's Laws of Motion Prepared by Chris Chiaverina Chapter Contents Newton's Laws of Motion Applying Newton's Laws Friction Newton's Laws of Motion Two of the most important

More information

Chapter 6 Dynamics I: Motion Along a Line

Chapter 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

Force a push or a pull exerted on some object the cause of an acceleration, or the change in an objects velocity

Force a push or a pull exerted on some object the cause of an acceleration, or the change in an objects velocity Chapter 4 Physics Notes Changes in Motion Force a push or a pull exerted on some object the cause of an acceleration, or the change in an objects velocity Forces cause changes in velocity Causes a stationary

More information

Dynamics-Friction. 1. Which vector diagram best represents a cart slowing down as it travels to the right on a horizontal surface?

Dynamics-Friction. 1. Which vector diagram best represents a cart slowing down as it travels to the right on a horizontal surface? 1. Which vector diagram best represents a cart slowing down as it travels to the right on a horizontal surface? Base your answers to questions 2 and 3 on the information A student and the waxed skis she

More information

Lesson 14: Friction. a) Fill in the table that follows by constructing a force diagram for the block (the system) for these five situations.

Lesson 14: Friction. a) Fill in the table that follows by constructing a force diagram for the block (the system) for these five situations. Lesson 14: Friction 14.1 Observe and Find a Pattern Perform the following experiment: Rest a wooden block (or some other object, like your shoe) on a table. Attach a large spring scale to a string attached

More information

1. A sphere with a radius of 1.7 cm has a volume of: A) m 3 B) m 3 C) m 3 D) 0.11 m 3 E) 21 m 3

1. A sphere with a radius of 1.7 cm has a volume of: A) m 3 B) m 3 C) m 3 D) 0.11 m 3 E) 21 m 3 1. A sphere with a radius of 1.7 cm has a volume of: A) 2.1 10 5 m 3 B) 9.1 10 4 m 3 C) 3.6 10 3 m 3 D) 0.11 m 3 E) 21 m 3 2. A 25-N crate slides down a frictionless incline that is 25 above the horizontal.

More information

Review 3: Forces. 1. Which graph best represents the motion of an object in equilibrium? A) B) C) D)

Review 3: Forces. 1. Which graph best represents the motion of an object in equilibrium? A) B) C) D) 1. Which graph best represents the motion of an object in equilibrium? A) B) C) D) 2. A rock is thrown straight up into the air. At the highest point of the rock's path, the magnitude of the net force

More information

Chapter 4. Forces and Newton s Laws of Motion. continued

Chapter 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 information

What is a Force? Free-Body diagrams. Contact vs. At-a-Distance 11/28/2016. Forces and Newton s Laws of Motion

What 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 information

Newton s 3 Laws of Motion

Newton s 3 Laws of Motion Newton s 3 Laws of Motion 1. If F = 0 No change in motion 2. = ma Change in motion Fnet 3. F = F 1 on 2 2 on 1 Newton s First Law (Law of Inertia) An object will remain at rest or in a constant state of

More information

Physics Chapter 4 Newton s Laws of Motion

Physics Chapter 4 Newton s Laws of Motion Physics Chapter 4 Newton s Classical Mechanics Classical Mechanics Describes the relationship between the motion of objects in our everyday world and the forces acting on them Conditions when Classical

More information

Physics 23 Exam 2 March 3, 2009

Physics 23 Exam 2 March 3, 2009 Use the following to answer question 1: A stationary 4-kg shell explodes into three pieces. Two of the fragments have a mass of 1 kg each and move along the paths shown with a speed of 10 m/s. The third

More information

Lecture Notes Chapter 5 Friction

Lecture Notes Chapter 5 Friction Lecture Notes Chapter 5 Friction NORMAL FORCES When an object rests on a surface, the surface exerts a normal force on the object, keeping it from accelerating downward. A normal force is perpendicular

More information

Chapter 5. Preview. Section 1 Measuring Motion. Section 2 What Is a Force? Section 3 Friction: A Force That Opposes Motion

Chapter 5. Preview. Section 1 Measuring Motion. Section 2 What Is a Force? Section 3 Friction: A Force That Opposes Motion Matter in Motion Preview Section 1 Measuring Motion Section 2 What Is a Force? Section 3 Friction: A Force That Opposes Motion Section 4 Gravity: A Force of Attraction Concept Mapping Section 1 Measuring

More information

9/20/11. Physics 101 Tuesday 9/20/11 Class 8" Chapter " Weight and Normal forces" Frictional Forces"

9/20/11. Physics 101 Tuesday 9/20/11 Class 8 Chapter  Weight and Normal forces Frictional Forces Reading Quiz Physics 101 Tuesday 9/20/11 Class 8" Chapter 5.6 6.1" Weight and Normal forces" Frictional Forces" The force due to kinetic friction is usually larger than the force due to static friction.

More information

Review of Lectures 1, 2 and 3

Review of Lectures 1, 2 and 3 Physics 22000 General Physics Lecture 5 Applying Newton s Laws Fall 2016 Semester Prof. Matthew Jones 1 Review of Lectures 1, 2 and 3 Algebraic description of linear motion with constant acceleration:

More information

Physics 8 Monday, October 9, 2017

Physics 8 Monday, October 9, 2017 Physics 8 Monday, October 9, 2017 Pick up a HW #5 handout if you didn t already get one on Wednesday. It s due this Friday, 10/13. It contains some Ch9 (work) problems, some Ch10 (motion in a plane) problems,

More information

Forces. A Force is a push or a pull on an object. Forces can cause a resting object to move

Forces. A Force is a push or a pull on an object. Forces can cause a resting object to move 13.2 Forces Forces A Force is a push or a pull on an object Forces can cause a resting object to move Forces can cause a moving object to accelerate by changing its speed or its direction Measuring Force

More information

Isaac Newton ( ) 1687 Published Principia Invented Calculus 3 Laws of Motion Universal Law of Gravity

Isaac 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 information

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. Exam Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) You are standing in a moving bus, facing forward, and you suddenly fall forward as the

More information

Chapter 4. Table of Contents. Section 1 Changes in Motion. Section 2 Newton's First Law. Section 3 Newton's Second and Third Laws

Chapter 4. Table of Contents. Section 1 Changes in Motion. Section 2 Newton's First Law. Section 3 Newton's Second and Third Laws Forces and the Laws of Motion Table of Contents Section 1 Changes in Motion Section 2 Newton's First Law Section 3 Newton's Second and Third Laws Section 4 Everyday Forces Section 1 Changes in Motion Objectives

More information

PreClass Notes: Chapter 5, Sections 5.4,5.5

PreClass Notes: Chapter 5, Sections 5.4,5.5 PreClass Notes: Chapter 5, Sections 5.4,5.5 From Essential University Physics 3 rd Edition by Richard Wolfson, Middlebury College 2016 by Pearson Education, Inc. Narration and extra little notes by Jason

More information

Physics 2A Chapter 4: Forces and Newton s Laws of Motion

Physics 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 information

March 10, P12 Inclined Planes.notebook. Physics 12. Inclined Planes. Push it Up Song

March 10, P12 Inclined Planes.notebook. Physics 12. Inclined Planes. Push it Up Song Physics 12 Inclined Planes Push it Up Song 1 Bell Work A box is pushed up a ramp at constant velocity. Draw a neatly labeled FBD showing all of the forces acting on the box. direction of motion θ F p F

More information

General Physics I Spring Applying Newton s Laws

General 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 information

3/10/2019. What Is a Force? What Is a Force? Tactics: Drawing Force Vectors

3/10/2019. 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 information

Physics 4A Chapter 5: Force and Motion and Chapter 6: Dynamics I: Motion Along a Line

Physics 4A Chapter 5: Force and Motion and Chapter 6: Dynamics I: Motion Along a Line Physics 4A Chapter 5: Force and Motion and Chapter 6: Dynamics I: Motion Along a Line Conceptual Questions and Example Problems from Chapters 5 and 6 Conceptual Question 5.7 An object experiencing a constant

More information

SEE the list given for chapter 04 where Newton s laws were introduced.

SEE the list given for chapter 04 where Newton s laws were introduced. PH2213 : Examples from Chapter 5 : Applying Newton s Laws Key Concepts Newton s Laws (basically Σ F = m a ) allow us to relate the forces acting on an object (left-hand side) to the motion of the object,

More information

Forces and Newton s Laws Reading Notes. Give an example of a force you have experienced continuously all your life.

Forces and Newton s Laws Reading Notes. Give an example of a force you have experienced continuously all your life. Forces and Newton s Laws Reading Notes Name: Section 4-1: Force What is force? Give an example of a force you have experienced continuously all your life. Give an example of a situation where an object

More information

# x = v f + v & % ( t x = v

# x = v f + v & % ( t x = v Name: Physics Chapter 4 Study Guide ----------------------------------------------------------------------------------------------------- Useful Information: F = ma µ = F fric a = v f " v i t # x = v f

More information

You may use g = 10 m/s 2, sin 60 = 0.87, and cos 60 = 0.50.

You may use g = 10 m/s 2, sin 60 = 0.87, and cos 60 = 0.50. 1. A child pulls a 15kg sled containing a 5kg dog along a straight path on a horizontal surface. He exerts a force of a 55N on the sled at an angle of 20º above the horizontal. The coefficient of friction

More information

What Is a Force? Slide Pearson Education, Inc.

What Is a Force? Slide Pearson Education, Inc. 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 information

Review: Advanced Applications of Newton's Laws

Review: 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 information

SPH3U1 - Dynamics Problems Set 3

SPH3U1 - Dynamics Problems Set 3 SPH3U1 - Dynamics Problems Set 3 Problems 1. A force of 1.2 N [ ] is applied to an object of mass 1.5 kg. It accelerates at 0.50 m/s 2 [ ] along a surface. Determine the force of friction that is acting

More information

PHYSICS 231 Laws of motion PHY 231

PHYSICS 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 information

Chapter 4. The Laws of Motion

Chapter 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 information

Online homework #6 due on Tue March 24

Online homework #6 due on Tue March 24 Online homework #6 due on Tue March 24 Problem 5.22 Part A: give your answer with only 2 significant digits (i.e. round answer and drop less significant digits) 51 Equilibrium Question 52 1 Using Newton

More information

Forces Review! By Cole Shute, Anisa Patel, Will Bley, and Camille Lorenz

Forces Review! By Cole Shute, Anisa Patel, Will Bley, and Camille Lorenz Forces Review! By Cole Shute, Anisa Patel, Will Bley, and Camille Lorenz Review of Concepts -force is a vector (It has magnitude and direction). -Mass: the measure of inertia of a body -weight: force due

More information

Friction Can Be Rough

Friction Can Be Rough 9.1 Observe and Find a Pattern Friction Can Be Rough Perform 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 information

Newton s Laws. A force is simply a push or a pull. Forces are vectors; they have both size and direction.

Newton 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 information

LECTURE 11 FRICTION AND DRAG

LECTURE 11 FRICTION AND DRAG LECTURE 11 FRICTION AND DRAG 5.5 Friction Static friction Kinetic friction 5.6 Drag Terminal speed Penguins travel on ice for miles by sliding on ice, made possible by small frictional force between their

More information

Forces and Newton s Laws

Forces and Newton s Laws chapter 3 section 1 Forces Forces and Newton s Laws What You ll Learn how force and motion are related what friction is between objects the difference between mass and weight Before You Read When you hit

More information

Forces. A Force is a push or a pull on an object. Forces can cause a resting object to move

Forces. A Force is a push or a pull on an object. Forces can cause a resting object to move 13.2 Forces Forces A Force is a push or a pull on an object Forces can cause a resting object to move Forces can cause a moving object to accelerate by changing its speed or its direction Measuring Force

More information

Physics 207 Lecture 7. Lecture 7

Physics 207 Lecture 7. Lecture 7 Lecture 7 "Professor Goddard does not know the relation between action and reaction and the need to have something better than a vacuum against which to react. He seems to lack the basic knowledge ladled

More information

ConcepTest PowerPoints

ConcepTest PowerPoints ConcepTest PowerPoints Chapter 4 Physics: Principles with Applications, 6 th edition Giancoli 2005 Pearson Prentice Hall This work is protected by United States copyright laws and is provided solely for

More information

Unit 1: Equilibrium and Center of Mass

Unit 1: Equilibrium and Center of Mass Unit 1: Equilibrium and Center of Mass FORCES What is a force? Forces are a result of the interaction between two objects. They push things, pull things, keep things together, pull things apart. It s really

More information

AP Physics 1 Review. On the axes below draw the horizontal force acting on this object as a function of time.

AP Physics 1 Review. On the axes below draw the horizontal force acting on this object as a function of time. P Physics Review. Shown is the velocity versus time graph for an object that is moving in one dimension under the (perhaps intermittent) action of a single horizontal force. Velocity, m/s Time, s On the

More information

Ch 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 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 information

Isaac Newton ( )

Isaac Newton ( ) Isaac Newton (1642-1727) In the beginning of 1665 I found the rule for reducing any degree of binomial to a series. The same year in May I found the method of tangents and in November the method of fluxions

More information

University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page 1

University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page 1 University Physics (Prof. David Flory) Chapt_06 Saturday, October 06, 2007 Page 1 Name: Date: 1. A crate resting on a rough horizontal floor is to be moved horizontally. The coefficient of static friction

More information

4. The diagram below shows a 4.0-kilogram object accelerating at 10. meters per second 2 on a rough horizontal surface.

4. The diagram below shows a 4.0-kilogram object accelerating at 10. meters per second 2 on a rough horizontal surface. 1. An 8.0-newton wooden block slides across a horizontal wooden floor at constant velocity. What is the magnitude of the force of kinetic friction between the block and the floor? A) 2.4 N B) 3.4 N C)

More information

AP 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). 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 information

Newton s First Law and IRFs

Newton s First Law and IRFs Goals: Physics 207, Lecture 6, Sept. 22 Recognize different types of forces and know how they act on an object in a particle representation Identify forces and draw a Free Body Diagram Solve 1D and 2D

More information

Applying Newton s Laws

Applying Newton s Laws Chapter 5 Applying Newton s Laws PowerPoint Lectures for University Physics, Twelfth Edition Hugh D. Young and Roger A. Freedman Lectures by James Pazun Goals for Chapter 5 To use and apply Newton s Laws

More information

PHY131H1F - Class 9. Today, finishing Chapter 5: Kinetic Friction Static Friction Rolling without slipping (intro) Drag

PHY131H1F - Class 9. Today, finishing Chapter 5: Kinetic Friction Static Friction Rolling without slipping (intro) Drag PHY131H1F - Class 9 Today, finishing Chapter 5: Kinetic Friction Static Friction Rolling without slipping (intro) Drag Microscopic bumps and holes crash into each other, causing a frictional force. Kinetic

More information

Friction (static & Kinetic) Review

Friction (static & Kinetic) Review Friction (static & Kinetic) Review 1. Sand is often placed on an icy road because the sand A) decreases the coefficient of friction between the tires of a car and the road B) increases the coefficient

More information

Chapter: The Laws of Motion

Chapter: The Laws of Motion Table of Contents Chapter: The Laws of Motion Section 1: Newton s Second Law Section 2: Gravity Section 3: The Third Law of Motion 1 Newton s Second Law Force, Mass, and Acceleration Newton s first law

More information

Friction Can Be Rough

Friction 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 information

Solution of HW4. and m 2

Solution of HW4. and m 2 Solution of HW4 9. REASONING AND SOLUION he magnitude of the gravitational force between any two of the particles is given by Newton's law of universal gravitation: F = Gm 1 m / r where m 1 and m are the

More information

Forces on an inclined plane. And a little friction too

Forces on an inclined plane. And a little friction too Forces on an inclined plane And a little friction too The Takeaway } You should be able to: } 2.2.2 Identify the forces acting on an object } Forces on non-horizontal surfaces } Including Friction } 2.2.8

More information

CHAPTER 4 TEST REVIEW -- Answer Key

CHAPTER 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 information

Can You Snap a Card Out From Under a Coin?

Can You Snap a Card Out From Under a Coin? Can You Snap a Card Out From Under a Coin? 1. Balance half of a 3 x 5 index card on the tip of an index finger. 2. Place a penny on the card, just above your fingertip. 3. Give the card a quick horizontal

More information

Section 3: Motion and Force. Preview Key Ideas Bellringer Fundamental Forces Balanced and Unbalanced Forces The Force of Friction Friction and Motion

Section 3: Motion and Force. Preview Key Ideas Bellringer Fundamental Forces Balanced and Unbalanced Forces The Force of Friction Friction and Motion : Motion and Force Preview Key Ideas Bellringer Fundamental Forces Balanced and Unbalanced Forces The Force of Friction Friction and Motion Key Ideas What do scientists identify as the fundamental forces

More information

AP Physics 1 - Test 05 - Force and Motion

AP 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 information

Lecture 6. Applying Newton s Laws Free body diagrams Friction

Lecture 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 information

Study Questions/Problems Week 4

Study Questions/Problems Week 4 Study Questions/Problems Week 4 Chapter 6 treats many topics. I have selected on average less than three problems from each topic. I suggest you do them all. Likewise for the Conceptual Questions and exercises,

More information

Topic 2: Mechanics 2.2 Forces

Topic 2: Mechanics 2.2 Forces Representing forces as vectors A force is a push or a pull measured in Newtons. One force we are very familiar with is the force of gravity, AKA the weight. The very concepts of push and pull imply direction.

More information

Physics Pre-comp diagnostic Answers

Physics Pre-comp diagnostic Answers Name Element Physics Pre-comp diagnostic Answers Grade 8 2017-2018 Instructions: THIS TEST IS NOT FOR A GRADE. It is to help you determine what you need to study for the precomps. Just do your best. Put

More information

REVISING MECHANICS (LIVE) 30 JUNE 2015 Exam Questions

REVISING MECHANICS (LIVE) 30 JUNE 2015 Exam Questions REVISING MECHANICS (LIVE) 30 JUNE 2015 Exam Questions Question 1 (Adapted from DBE November 2014, Question 2) Two blocks of masses 20 kg and 5 kg respectively are connected by a light inextensible string,

More information

Chapter 6. Applications of Newton s Laws

Chapter 6. Applications of Newton s Laws Chapter 6 Applications of Newton s Laws P. Lam 7_11_2018 Learning Goals for Chapter 5 Learn how to apply Newton s First Law & Second Law. Understand the cause of apparent weight and weightlessness Learn

More information

Question: Are distance and time important when describing motion? DESCRIBING MOTION. Motion occurs when an object changes position relative to a.

Question: Are distance and time important when describing motion? DESCRIBING MOTION. Motion occurs when an object changes position relative to a. Question: Are distance and time important when describing motion? DESCRIBING MOTION Motion occurs when an object changes position relative to a. DISTANCE VS. DISPLACEMENT Distance Displacement distance

More information

Four naturally occuring forces

Four naturally occuring forces Forces System vs Environment: system the object the force is applied to environment the world around the object that exerts the force Type Forces: Contact is applied by touching Long range exerted without

More information

Ch. 2 The Laws of Motion

Ch. 2 The Laws of Motion Ch. 2 The Laws of Motion Lesson 1 Gravity and Friction Force - A push or pull we pull on a locker handle push a soccer ball or on the computer keys Contact force - push or pull on one object by another

More information

Forces I. Newtons Laws

Forces I. Newtons Laws Forces I Newtons Laws Kinematics The study of how objects move Dynamics The study of why objects move Newton s Laws and Forces What is force? What are they? Force A push or a pull Symbol is F Unit is N

More information

Wiley Plus. Final Assignment (5) Is Due Today: Before 11 pm!

Wiley Plus. Final Assignment (5) Is Due Today: Before 11 pm! Wiley Plus Final Assignment (5) Is Due Today: Before 11 pm! Final Exam Review December 9, 009 3 What about vector subtraction? Suppose you are given the vector relation A B C RULE: The resultant vector

More information

5. Two forces are applied to a 2.0-kilogram block on a frictionless horizontal surface, as shown in the diagram below.

5. Two forces are applied to a 2.0-kilogram block on a frictionless horizontal surface, as shown in the diagram below. 1. The greatest increase in the inertia of an object would be produced by increasing the A) mass of the object from 1.0 kg to 2.0 kg B) net force applied to the object from 1.0 N to 2.0 N C) time that

More information

Chapter 4 Forces Newton s Laws of Motion

Chapter 4 Forces Newton s Laws of Motion Chapter 4 Forces Newton s Laws of Motion Forces Force A vector quantity that changes the velocity vector of an object. When you hit a baseball, the velocity of the ball changes. Can be a push or a pull

More information

Reading Quiz. Chapter 5. Physics 111, Concordia College

Reading 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 information

EQUATIONS OF MOTION: RECTANGULAR COORDINATES

EQUATIONS OF MOTION: RECTANGULAR COORDINATES EQUATIONS OF MOTION: RECTANGULAR COORDINATES Today s Objectives: Students will be able to: 1. Apply Newton s second law to determine forces and accelerations for particles in rectilinear motion. In-Class

More information