Skills Worksheet Directed Reading B Section: Newton s Laws of Motion NEWTON S FIRST LAW OF MOTION Part 1: Objects at Rest 1. Which is NOT an example of an object at rest? a. a golf ball on a tee b. a jet flying overhead c. a chair on a floor d. a picture on a wall Part 2: Objects in Motion 2. When will objects at rest NOT stay at rest? a. when there is no horizontal motion b. when there is no vertical motion c. when there is no friction d. when objects are acted upon by unbalanced forces Friction and Newton s First Law 3. What happens to your motion when the bumper car you re riding in is hit? a. Your motion stops. b. Your motion continues with less velocity. c. Your motion continues with the same velocity. d. Your motion continues with greater velocity. 4. Why will the soccer ball you kick come to a stop on its own? a. It is stopped by friction. b. You haven t kicked it hard enough. c. It is stopped by gravity. d. The ball is worn out. Holt Science and Technology 14 Forces and Motion
Inertia and Newton s First Law 5. Why can t a car, plane, or bicycle stop immediately? a. air resistance b. friction c. inertia d. gravity Mass and Inertia 6. Why is it easier to stop a bicycle than a car? a. The bicycle has smaller mass and more inertia. b. The bicycle has smaller mass and thus has less inertia. c. The car has greater mass and thus less inertia. d. The car is harder to drive. NEWTON S SECOND LAW OF MOTION Part 1: Acceleration Depends on Mass 7. Why does it take more force to accelerate a full grocery cart than an empty one? a. The full cart has more mass. b. The full cart is harder to steer. c. The empty cart has more mass. d. You run into air resistance. Part 2: Acceleration Depends on Force 8. If you give a cart a harder push, what happens to its acceleration? a. It decreases. b. It increases. c. It stays the same. d. It varies. Holt Science and Technology 15 Forces and Motion
Expressing Newton s Second Law Mathematically 9. Why is a watermelon harder to accelerate than an apple? a. The watermelon is harder to grip. b. The apple has greater mass. c. You can hold an apple in one hand. d. The watermelon has greater mass. 10. Which of the following is the equation for Newton s second law of motion? a. F m a b. F m a c. F m a d. F g t NEWTON S THIRD LAW OF MOTION 11. Which is a simple way to describe Newton s third law of motion? a. Acceleration depends on the force applied to a mass. b. All forces act in pairs. c. An object at rest remains at rest unless acted on by a force. d. A moving object remains in motion at constant speed unless acted on by a force. Force Pairs Do Not Act on the Same Object 12. What would happen if the action and reaction forces acted on the same object? a. The object would move in the direction of the action force. b. The object would move in the direction of the reaction force. c. The result cannot be predicted. d. The forces would cancel and the object does not move. Holt Science and Technology 16 Forces and Motion
All Forces Act in Pairs Action and Reaction 13. What is the reaction force pushing on a jumping rabbit s legs? a. friction c. Earth pushing upwards b. gravity d. The rabbit pushing on Earth 14. During a space shuttle take off, what is the reaction force that sends it into space? a. Earth s gravity b. the shuttle s thrusters pushing on exhaust gases c. the gases pushing downward d. the gases pushing the shuttle upward. 15. Why doesn t the bat move backwards, when the ball hits it? a. Because the bat exerts an action force on the ball. b. Because the ball exerts a reaction force on the bat. c. Because the batter exerts another force on the bat. d. Because the ball flys off the bat. The Effect of a Reaction Can Be Difficult to See 16. When you drop a ball, what is the action force on the ball? a. the ball s gravity b. Earth gravity c. friction between the ball and Earth d. your weight 17. When you drop a ball, what is the reaction force on the Earth? a. the ball s gravity b. Earth s gravity c. friction between the ball and Earth d. your weight Holt Science and Technology 17 Forces and Motion
TEACHER RESOURCE PAGE 15. The action force is your weight pushing down on the chair. The reaction force is the force exerted by the chair that pushes up on your body and is equal to your weight. 16. The hands of the swimmer pushing against the water is the action force. The reaction force is the water pushing on the hands, which is the force that moves the swimmer forward. 17. The bat doesn t move backwards because the batter is exerting another force on the bat. 18. It is hard to see the effect of the reaction force, which is the Earth being pulled upward., because Earth s mass is so much larger than the ball s mass. Earth s acceleration is thus so small, you can t see or feel it. SECTION: MOMENTUM 1. The truck has more mass, and thus more momentum, than the car has. The truck needs a larger force to stop it. 2. momentum 3. the faster car 4. By multiplying the value for mass of the automobile by its the velocity, its momentum can be calculated. 5. Kilograms multiplied by meters per second, or Kg m/s. 6. C 7. B 8. the law of conservation of momentum 9. Because the combined mass of the board and skateboarder is greater than the mass of the skateboarder alone, the velocity of the skateboarder and board must be less than that of the skateboarder alone. When mass increases, velocity decreases. 10. Momentum is transferred from one object to another, causing objects to move in different directions at different speeds. But the total momentum of all objects stays the same. 11. The action force of the cue ball on the billiard ball, and the reaction force of the billiard ball on the cue ball, are equal and opposite. Momentum is not gained or lost. Directed Reading B SECTION: GRAVITY AND MOTION 1. C 2. B 3. A 4. B 5. B 6. C 7. A 8. air resistance 9. terminal velocity 10. free fall 11. B 12. C 13. A 14. B 15. A 16. C 17. D 18. B 19. C 20. C 21. A SECTION: NEWTON S LAWS OF MOTION 1. B 2. D 3. C 4. A 5. C 6. B 7. A 8. C 9. D 10. C 11. B 12. D 13. B 14. D 15. C 16. B 17. A SECTION: MOMENTUM 1. B 2. A 3. C 4. D 5. C 6. A 7. B Holt Science and Technology 97 Forces and Motion