FORCE & MOTION Instructional Module 6 Dr. Alok K. Verma Lean Institute - ODU 1
Description of Module Study of different types of forces like Friction force, Weight force, Tension force and Gravity. This Module studies relationship between forces and the different types of Motion they produce, using Newton s three laws of Motion. Dr. Alok K. Verma Lean Institute - ODU 2
Targeted Sols : A-1, 3, 11, 15,G -3, 4, 9, AII-2,3,T-3, AII/T-3, AII/T-2 PH - 5d, 5C, 5E Learning objectives Activity Force and motion Tension Hooke's law Projectile motion Gravity Identify the forces that cause an object s motion Calculate tension on string and force acting on it. To verify Hooke's law relation ship between force and elongation How projectile angle effects range and velocity on different masses. Calculate weight on different planets Acceleration Dr. Alok K. Verma Lean Institute - ODU Calculate acceleration on connected objects 3
Topics Covered No Topic Time 1. Force and Motion 2. Balanced and Unbalanced forces 3. Types of Forces 4. Types of Friction. 5. Tension Force 6. Hooke s law 7. Gravity 8. Mass and Weight 9. Newton's First Law 10. Newton's Second Law 11. Newton's Third Law Dr. Alok K. Verma Lean Institute - ODU 4
Force &Motion Force: A push or pull that one body exerts on another. Motion: A Change of Position or Location. Dr. Alok K. Verma Lean Institute - ODU 5
Unit of Force Forces are measured in Newton A Newton is the force required to give a mass of 1 kilogram (1 kg) an acceleration of 1 meter per second per second (1 m/s 2 ). It is abbreviated as N. 1 N is equivalent to 1 kg-m/s 2. Dr. Alok K. Verma Lean Institute - ODU 6
Different Ways of Measuring Force 1. Spring Scale 2. Force Meter 3. Force Gauges a) Mechanical Gauges b) Digital Gauges 4. Dynamometer Dr. Alok K. Verma Lean Institute - ODU 7
Balanced Forces Balanced forces do not cause change in motion They are equal in size and opposite in direction F F F F Dr. Alok K. Verma Lean Institute - ODU 8
Unbalanced Forces An unbalanced force always causes a change in motion They are not equal in size and opposite in direction F F 2F 2F Dr. Alok K. Verma Lean Institute - ODU 9
Which one is balanced and unbalanced? 4 N, left 4 N, right 4 N, left 10 N, right Dr. Alok K. Verma Lean Institute - ODU 10
Answers Which one is balanced and unbalanced? 4 N, left 4 N, right Balanced 4 N, left 10 N, right Unbalanced Dr. Alok K. Verma Lean Institute - ODU 11
Types of Forces 1. Normal force 2. Friction Force 3. Tension force 4. Gravitational Force 5. Spring Force 6. Electromagnetic Force 7. Nuclear force Dr. Alok K. Verma Lean Institute - ODU 12
Normal Force It is the force exerted by one surface on another. It is perpendicular to the surface. Normal Force (F n ) Friction Force (F f ) Weight of block (W) Dr. Alok K. Verma Lean Institute - ODU 13
The person is walking on the floor and he slips suddenly. What is the reason? Because of lack of Friction Dr. Alok K. Verma Lean Institute - ODU 14
Friction Force Force that opposes motion between two surfaces. Depends on the: types of surfaces different materials Friction force (F f ) F f = m F n Normal force (F n ) Coefficient of friction Dr. Alok K. Verma Lean Institute - ODU 15
Four Types of Friction 1. Static Friction: Force that acts on objects that are not moving Dr. Alok K. Verma Lean Institute - ODU 16
Four Types of Friction 2. Sliding Friction: Force resulting when pushing or pulling an object over a surface MarineTech Dr. Alok K. Verma Lean Institute - ODU 17
Four Types of Friction 3. Rolling Friction: is the resistance that occurs when a round object such as a ball or tire rolls on a flat surface. Much easier to move object. Dr. Alok K. Verma Lean Institute - ODU 18
Four Types of Friction 4. Fluid Friction: Solid moving through a liquid or a gas Force of a fluid friction is always less than sliding friction The resistance that a body experiences in fluid is knows as Drag force. This is proportional to square of velocity of a body. Dr. Alok K. Verma Lean Institute - ODU 19
Coefficient of Friction Coefficient of Friction (µ) (mu): It is the ratio of the force of friction between two bodies and the force pressing them together. We use the symbol µ (Greek alphabet). Value of µ depends on the two surfaces involved and material they are made up of. Example: Teflon on steel has a low coefficient of friction. µ = 0.04 Rubber on concrete has a high coefficient of friction. µ = 1.0 Dr. Alok K. Verma Lean Institute - ODU 20
Calculation of Coefficient of Friction Coefficient of Friction (µ) can be calculated experimentally by the following formula: Normal Force (F n ) Friction Force (F f ) µ = Height/ Length Height Dr. Alok K. Verma Lean Institute - ODU Length Weight of block (W) 21
1. The direction of friction is always to the direction in which the object is moving. a. Same b. Opposite c. Unrelated 2. When an object is moving faster through a fluid what happens to the force of friction on it? a. Force of Friction increases. b. Force of Friction decreases. c. There is no force. Dr. Alok K. Verma Lean Institute - ODU 22
1. The direction of friction is always to the direction in which the object is moving. a. Same b. Opposite c. Unrelated 2. When an object is moving faster through a fluid what happens to the Drag force? a. Drag Force increases. b. Drag Force decreases. c. There is no force. Answers Dr. Alok K. Verma Lean Institute - ODU 23
Hands on Activity - 1 Measure Coefficient of Friction Dr. Alok K. Verma Lean Institute - ODU 24
MarineTech Objective: Measuring the coefficient of friction between different surfaces. Materials for class activity: 1. A Flat corrugated plastic board to be used as a ramp. 2. Square block with six different surfaces.(copper,brass,rubber, Wood(Rough surface),wood(smooth Surface),Cork sheet. 3. 12 Ruler. 4. 3 dowels. 5. Base Stand. Hands on Activity - 1 Measure Coefficient of Friction 6. Square beam with pulley. 7. Wooden clamp Dr. Alok K. Verma Lean Institute - ODU 25
Assembled Equipment: Dr. Alok K. Verma Lean Institute - ODU 26
Activity Procedure: 1. Put the square block on the top of the ramp in the center with the surface materials in contact according to the worksheet. 2. Gently release the clamp and slide down the centre post raising the ramp until the block starts to slide. 3. Lock the clamp in this position. 4. Measure the height and length of the inclined plane and enter in the work sheet. 5. Calculate the coefficient of friction between the surfaces using the formula: µ = Height/Length 6. Repeat the steps for other five surfaces on the block and record height and length on the worksheet for each surface combination. Dr. Alok K. Verma Lean Institute - ODU 27
S.No Slide surface material Block Surface material 1 Plastic Copper Work Sheet Length Height Average Length Average Height MarineTech Coefficient of Friction = Height/Length 2 Plastic Brass 3 Plastic Rubber 4 Plastic Wood (Rough Surface) 5 Plastic Wood (smooth) 6 Plastic Cork Dr. Alok K. Verma Lean Institute - ODU
Tension Force Tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object The tension force is directed along the length of the wire and pulls equally on the objects on the opposite ends of the wire. Dr. Alok K. Verma Lean Institute - ODU 29
Hands on Activity - 2 Tension Force Objective: Calculate Tension force in the string and observe in the tension protractor. Materials for class activity: 1. Tension Protractor 2. Vertical Square stick 3. Ruler. 4. String. 5. Weight 300 grams. 6. Weight 200 grams. 7. Weight 100 grams. Dr. Alok K. Verma Lean Institute - ODU 30
T = Tension in the string F = Force in the horizontal arm Hands on Activity - 2 Tension Force MarineTech Free Body Diagram T T Y θ Y X F θ X W= mg W= mg Sum of all the forces in the x and y direction should be zero Dr. Alok K. Verma Lean Institute - ODU 31
Hands on Activity - 2 Free Body Diagram Tension Force Sum of all the forces in the y T Y direction F y = 0 T Sin(θ) W = 0 F θ W= mg T = Tension in the string F = Force in the horizontal arm X MarineTech Sum of all the forces in the x direction F x = 0 F T Cos(θ) = 0 Sum of all the forces in the x and y direction should be zero Dr. Alok K. Verma Lean Institute - ODU 32
Work Sheet Suspended Mass (kg) W = mg (N) F y = 0 T Sin(θ) W = 0 Tension (T) (N) F x = 0 F T Cos(θ) = 0 Force (F) (N) 0.3 0.2 0.1 Dr. Alok K. Verma Lean Institute - ODU 33
Hands on Activity - 2 Tension Force Dr. Alok K. Verma Lean Institute - ODU 34
10 Minutes Dr. Alok K. Verma Lean Institute - ODU
Gravity Force of attraction between any two objects in the universe. Gravity Force Increases As mass increases As distance decreases between two objects g earth = 9.81m/s 2 Dr. Alok K. Verma Lean Institute - ODU 36
MASS & WEIGHT Mass: Mass is a measure of matter. Mass is constant. m = mass (kg) Weight: Weight is a force. Weight is not constant. The weight of an object depends on location with respect to the Earth s surface W = mg W = Weight (N) m = Mass (kg) g = Acceleration due to gravity(m/s 2 ) Dr. Alok K. Verma Lean Institute - ODU 37
Comparison of Weight on Earth and Mars Dr. Alok K. Verma Lean Institute - ODU 38
Class Exercise - 1 To find gravity force on different Planets Dr. Alok K. Verma Lean Institute - ODU 39
1. The amount of matter in an object is called its weight a. True b. False 2. The mass of an object is 20 kg on earth, its weight is a. 196 N b. 200 N c.76 N d. 96 N 3. An object has a weight of 30 N on earth. A second object weighs 30 N on the moon, which object has greater mass? a. The one on the earth b. They have the same mass c. The one on the moon d. Not enough information provided Dr. Alok K. Verma Lean Institute - ODU 40
Answers 1. The amount of matter in an object is called its weight a. True b. False 2. The mass is 20 kg on earth and its weight is a. 196N b. 200N c. 76N d. 96N 3. An object has a weight of 30N on earth. A second object weighs 30N on the moon, which object has greater mass? a. The one on the earth b. They have the same mass c. The one on the moon d. Not enough information provided Dr. Alok K. Verma Lean Institute - ODU 41 41
Hooke's Law MarineTech It states that the Elongation of a spring is in direct proportion with the load added to it as long as this load does not exceed the elastic limit. Elastic Limit: The maximum stress that can be applied to a Spring without producing permanent deformation Force (N) F = k x Elongation (m) Spring Stiffness (N/m) Dr. Alok K. Verma Lean Institute - ODU 42
Hands on Activity - 3 Hooke's Law Objective: To verify Hooke's Law (Relation between force & Elongation) MarineTech Materials for class activity: 1. 10N/m Spring 2. 20N/m Spring 3. 40N/m Spring 4. Weights (5 Hooke's law apparatus 5. 50g, 100g, 200g and 500g) Dr. Alok K. Verma Lean Institute - ODU 43
Activity Procedure: 1. Hang the 10 N (Red) spring from the notch on the support arm 2. Align the top surface of the washer with zero on the scale 3. Hang the specified weight from the spring 4. Measure the stretch of the spring and note the values in the work sheet 5. Repeat the steps for additional weights according to the worksheet 6. Repeat the above steps for 20 N (Blue) and 40 N (Green) spring. Dr. Alok K. Verma Lean Institute - ODU 44
No 1 2 3 4 Spring Stiffness 10 N/m Work Sheet Weights (grams) Force(N) Elongation(cm) No 1 2 3 4 Spring Stiffness 20 N/m Weights (grams) Force(N) Elongation(cm) Spring Stiffness 40 N/m No Weights (grams) Force(N) Elongation(cm) 1 2 3 4 Dr. Alok K. Verma Lean Institute - ODU 45
Hands on Activity - 3 To Verify Hooke s Law (Relationship between Force & Elongation) Dr. Alok K. Verma Lean Institute - ODU 46
VELOCITY Velocity: Velocity is the rate of change of position The velocity v of an object moving through a displacement (Δ x) during a time interval (Δ t) is described by the formula: Velocity Total Displacement Travel Time Units = meters/sec Dr. Alok K. Verma Lean Institute - ODU 47
ACCELERATION Acceleration: Acceleration is defined as the rate of change of velocity. The acceleration is the ratio between the change in velocity and the time interval. Accelerati on Change in velocity Travel Time Units = meters/sec 2 Dr. Alok K. Verma Lean Institute - ODU 48
Height(H) MarineTech Projectile Motion When an object is thrown into the air, its motion is affected by gravity and wind resistance. It follows a parabolic path as shown on the right. At the maximum height, the vertical component of velocity becomes zero and changes direction. V X V Y Dr. Alok K. Verma Lean Institute - ODU Range 49
Slow projectile - shoot a monkey Fast projectile - shoot a monkey Fast Projectiles travel longer distances Dr. Alok K. Verma Lean Institute - ODU 50
Hands-on Activity - 4 Projectile Motion Objective: To observe how projectile angle affects distance and velocity of different masses. Materials for Class Activity: 1.Catapault 2. Two balls of different masses. (17 grams, 25 grams) 3. Stop Watch 4. Measuring Tape Dr. Alok K. Verma Lean Institute - ODU 51
Activity Procedure: 1. Arrange the equipment such that the ball will land in a safe area by calculating the maximum distance it might travel 2. Place the ball in the catapult 3. Start the gun of the catapult at 38 degrees 4. Release the ball and note down the time taken when it touches the ground by using Stop watch 5. Repeat the Step 4 for angles 62, 84 and note down the values in worksheet 1 provided Dr. Alok K. Verma Lean Institute - ODU 52
Free Body Diagram Assembled Equipment: V V y V x V = Velocity V x = Velocity in Horizontal direction V y = Velocity in Vertical direction Dr. Alok K. Verma Lean Institute - ODU 53
NO Mass = 17 grams Angle(θ ) degrees 1 38 2 62 3 84 Distance (meters) D 1 D 2 T 1 T 2 Work Sheet Time of flight(sec) V x = V Cos(θ) MarineTech Mass = 25 grams NO Angle(θ) degrees Distance (meters) D 1 D 2 T 1 T 2 Time of flight(sec) V x = V Cos(θ) 1 38 2 62 3 84 Dr. Alok K. Verma Lean Institute - ODU 54
Hands on activity - 4 Projectile Motion Dr. Alok K. Verma Lean Institute - ODU 55
15 Minutes Dr. Alok K. Verma Lean Institute - ODU
Inertia The tendency of all objects to resist any change in motion. More mass= More inertia Harder to start or stop motion of an object. Less mass = Less inertia Easier to start or stop motion an object Dr. Alok K. Verma Lean Institute - ODU 57
NEWTON S FIRST LAW An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. No force FORCE Dr. Alok K. Verma Lean Institute - ODU 58
NEWTON S FIRST LAW These pumpkins will not move unless acted on by an unbalanced force. Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever. Dr. Alok K. Verma Lean Institute - ODU 59
1. The inertia applies to a. Objects that are not moving b. Moving objects c. Both moving & non moving objects 2. An object wants to maintain its state of motion because it has a. Inertia b. Velocity c. Speed d. Acceleration 3. Why then, do we observe every day objects in motion slowing down and becoming motionless seemingly without an outside force? Dr. Alok K. Verma Lean Institute - ODU 60
1. The inertia applies to Answers a. Objects that are not moving b. Moving objects c. Both moving & non moving objects 2. An object wants to maintain its state of motion because it has a. Inertia b. Velocity c. Speed d. Acceleration 3. Why then, do we observe every day objects in motion slowing down and becoming motionless seemingly without an outside force? Ans: It s a force we sometimes cannot see Friction. Dr. Alok K. Verma Lean Institute - ODU 61
Newton s Second Law The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. F a m F m net F net F ma Dr. Alok K. Verma Lean Institute - ODU 62
1. Acceleration is produced by a. Forces b. acceleration c. Pressures d. velocities e. masses 2. Mary is accelerating her little red wagon when Tom begins to pull in the same direction effectively doubling the net force on the wagon what happens to the Wagons acceleration? a. It halves b. It doubles c. It quarters d. It stays the same Dr. Alok K. Verma Lean Institute - ODU 63
Answers 1. Acceleration is produced by a. Forces b. acceleration c. Pressures d. velocities e. masses 2. Mary is accelerating her little red wagon when tom begins to pull in the same direction effectively doubling the net force on the wagon what happens to the Wagons acceleration? a. It halves b. It doubles c. It quarters d. It stays the same Dr. Alok K. Verma Lean Institute - ODU 64 64
Class Exercise - 2 Find Force, Mass, Acceleration in the given problems Dr. Alok K. Verma Lean Institute - ODU 65
Hands on Activity - 5 Acceleration Objective: To study the impact of force on the acceleration of a cart under varying load conditions Case 1: Mass of cart constant, Varying force. Case 2: Force constant,mass of cart varying. Materials for class activity 1. Motion sensor 2. Wooden track 3. Wooden cart 4. Mass hanger 5. Washers (mass = 34 grams = 0.034 kgs) MarineTech Dr. Alok K. Verma Lean Institute - ODU 66
Assembled Equipment: Dr. Alok K. Verma Lean Institute - ODU
MarineTech Activity procedure: Case - 1 1. Place one washer on the mass hanger. 2. Pull the cart back so the mass is just below the pulley. 3. Make sure that the cart is at least 15cm away from the motion sensor. 4. Tap play button to start recording data and release the cart so it moves toward the pulley. 5. Tap stop button to stop recording after it reaches at the end of the track. 6. Record the value of acceleration from Spark and note it in the last column. 7. Place a second washer on the mass hanger and repeat steps 2 to 6. 8. Place a third washer on the mass hanger and repeat steps 2 to 6. Dr. Alok K. Verma Lean Institute - ODU 68
Work sheet Case - 1 Mass of the Cart Constant, Varying Force Suspended Mass M 1 (KG) W 1 =M 1 g=n 1 (Newton) Cart on track M 2 (Kg) W 2 =M 2 g=n 2 (Newton) F=µN 2 (Newton) T=M 2 a+f Theoretical value a=w 1 -T/M 1 (m/s 2 ) Experiment values of a (m/s 2 ) Force = Mass * 9.81N Mass of the cart = 131 grams. Mass of the washer = 34 grams. Coefficient of friction = 0.2 Dr. Alok K. Verma Lean Institute - ODU 69
MarineTech Case -2 1. Place two washers in the mass hanger. 2. Pull the cart back so the mass is just below the pulley. 3. Make sure that the cart is at least 15 cm away from the motion sensor. 4. Tap play button to start recording data and release the cart so it moves toward the pulley. 5. Tap stop button to stop recording after it reaches at the end of the track. 6. Record the value of acceleration from Spark and note it in the last column. 7. Place one washer on the top of the cart and repeat steps 2 to 6. 8. Place a Second washer on top of the cart and repeat steps 2 to 6. Dr. Alok K. Verma Lean Institute - ODU 70
Suspended Mass M 1 (KG) W 1 =M 1 g=n 1 (Newton) Work sheet - 2 Mass Cart Varying and Force Constant Cart on track M 2 (Kg) W 2 =M 2 g=n 2 (Newton) F=µN 2 (Newton) T=M 2 a+f Theoretical value a=w 1 -T/M 1 (m/s 2 ) MarineTech Experiment values of a (m/s 2 ) Force = Mass*9.81N Mass of the cart = 131 grams. Mass of the washer = 34 grams. Coefficient of friction = 0.2. Dr. Alok K. Verma Lean Institute - ODU 71
Hands on Activity - 5 Acceleration of Connected Objects Dr. Alok K. Verma Lean Institute - ODU 72
Newton s Third Law For every action there is an equal and opposite reaction Dr. Alok K. Verma Lean Institute - ODU 73
Action-Reaction Example F G The rocket exerts a downward force on the exhaust gases The gases exert on equal but opposite upward force on the rocket F R Dr. Alok K. Verma Lean Institute - ODU 74
Class Exercise - 3 Complete the table by writing the reaction for each action. Dr. Alok K. Verma Lean Institute - ODU 75
Class Exercise - 4 Solve the word puzzle and match the following on force and motion. Dr. Alok K. Verma Lean Institute - ODU 76