Make sure you know the three laws inside and out! You must know the vocabulary too!

Transcription

1 Newton's Laws Study Guide Test March 9 th The best plan is to study every night for 15 to 20 minutes. Make sure you know the three laws inside and out! You must know the vocabulary too! Newton s First Law An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This law is often called "the law of inertia". Newton s Second Law Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). Newton s Third Law For every action there is an equal and opposite re-action. True/False Indicate whether the statement is true or false. 1. Gravity and magnetism are examples of contact forces. 2. Weight is the measure of gravitational force on an object. 3. Mass and weight are not related to each other. 4. Forces have strength and direction. 5. According to Newton s first law, the motion of an object does not change if the net force acting on it is zero. 6. If there were no friction, a moving object would keep moving, even if no other force were applied to it. 7. Inertia is two or more forces acting in opposite directions. 8. Only unbalanced forces change an object s velocity. 9. Centripetal force causes an object in circular motion to move along a straight path. 10. Unbalanced forces can cause an object in motion to accelerate. 11. If the direction of the net force acting on an object is opposite to the direction of movement, the object will speed up. 12. Force pairs act in opposite directions and are the same strength. 13. In a force pair, one force is the action force and the other force is the second force.

2 14. According to Newton s third law, when an object applies a force on a second object, the second object applies a weaker reaction force in response. 15. You can reduce friction by _. a. increasing mass b. removing lubricant c. reducing surface area. 16. Which type of friction exists between a surface and moving air? a. fluid friction b. static friction c. sliding friction 17. Which factor is NOT involved in determining gravitational force? a. Mass b. Speed c. distance 18. If one force of 30 N and another force of 85 N result in a net force of 55 N, which term describes the two forces? a. negative forces b. balanced forces c. unbalanced forces 19. Which term explains why a crash-test dummy lunges forward during a car crash? a. Inertia b. gravity c. velocity 20. What happens to an object at rest if balanced forces act upon it? a. The object remains at rest. b. The object begins to move at a constant speed. c. The object begins to move and then slows down. 21. If the reference direction is to the left and a force of 45 N acts to the left while another force of 65 N acts to the right, how much net force is acting on the object? a. 20 N b. 20 N c. 110 N 22. A ball held in a person s hand does not move, even though gravity is acting on it because _. a. the force of gravity creates a net unbalanced force b. the force of gravity is not strong enough to move the ball c. the force of gravity is balanced by the force exerted by the hand 23. According to Newton s second law of motion, which equation determines acceleration of an object? [a = acceleration; F = force; m = mass] a. a = b. a = c. a = m F

3 24. Which situation is NOT the result of an unbalanced force acting on an object? a. an object speeds up b. an object maintains speed c. an object changes direction 25. The law of conservation of momentum states that the total momentum of a group of objects _. a. increases after a collision b. decreases after a collision c. remains the same after a collision 26. When a gymnast performs, which force is most important in determining how high he or she jumps? a. the downward force of gravity b. the the friction exerted by the ground c. the action force that the gymnast exerts on the ground 27. Which term is a force that can slow momentum? a. mass b. inertia c. friction 28. Which type of force involves two objects touching? a. contact b. magnetic c. noncontact 29. What will happen to an object at rest if the net force acting on it is zero? a. It will speed up. b. It will stay at rest. c. It will start moving. 30. The formula acceleration = net force/mass applies to _. a. Newton s first law of motion b. Newton s third law of motion c. Newton s second law of motion 31. An astronaut s _ changes as he or she goes from Earth into space. a. Size b. Mass c. weight Matching Match each of the examples with correct Law of Motion. a. Newton s First Law b. Newton s Second Law c. Newton s Third Law 1. two football players collide and stick together 2. swinging a ball on a string around your head 3. a girl pushes a sled and the sled accelerates

4 4. a rocket takes off because the force from the engines pushes on the ground 5. a balloon flies off when the opening is released 6. gravity causes a ball to fall 7. magnets repel each other 8. the motion of a satellite as it orbits Earth 9. water pushes you forward when you push against it 10. a book sitting on the table Match each term with the correct definitions below. a. Force d. centripetal force b. Mass e. force pair c. inertia f. Momentum 11. tendency of an object to resist a change in motion 12. a push or a pull on an object 13. amount of matter in an object 14. measure of how hard it is to stop a moving object 15. forces that two objects apply on each other 16. acts perpendicular to the direction of motion when an object moves in a circle Match each term with the correct description below. Not all terms will be used a. force e. weight b. momentum f. inertia c. force pair g. centripetal force d. mass 17. the force that two objects exert on each other 18. the tendency of an object to resist a change in motion 19. a push or a pull on an object 20. the amount of matter in an object 21. the measure of how hard it is to stop a moving object 22. acts perpendicular to the direction of motion when an object moves in a circle Problem 1. Calculate the force on an object that has a mass of 12 kg and an acceleration of 4 m/s A top-fuel dragster accelerates from rest to a velocity of 100 m/s in 8 s. What is the acceleration?

5 3. On Planet Zorg, a 30-kg barbell can be lifted by only exerting a force of 180 N. What is the acceleration of gravity on Planet Zorg? 4. A racing car has a mass of 750 kg. It undergoes an acceleration of 4.00 m/s 2. What is the net force acting on the car?