2. Chapters 5-6 Test Review Forces & Motion

3. Forces  “a push or a pull”  A force can start an object in motion or change the motion of an object.  A force gives energy to an object

4. What is a push or a pull?  A. canopy  B. force  C. gruff  D. scoff

5. Representing forces  We often use arrows.  Larger the arrow, the greater the force  Combined balanced forces equal zero  Normal force = the force acting perpendicular on an object in contact with another object.

6. What prevents a book on a table from accelerating downward?  A. gravity is pulling on the table  B. the table is pushing back with a larger force  C. the table is pushing back with an equal force  D. air

7. Balanced Forces  Forces opposite in direction and equal in size.  Net result: no change in motion.

8.  Unbalanced forces will cause an object to change motion. Unbalanced Forces

9. When an unbalanced force acts on an object,  A. the object’s motion does not change.  B. the object accelerates.  C. the object will stop.  D. the inertia of the object increases.

10. The net forces acting on any object will cause it to  A. keep moving at the same speed.  B. accelerate.  C. stop.  D. swim like a fish.

11. If a 10 N net forces acts on a 20 kg object it will accelerate at (a=f/m)  A. 5 m/s  B. 200 m/s  C. 0.5 m/s 2  D. 2 m/s 2

12. What force is needed to accelerate a 4 kg ball at 12 m/s 2 ? (a=f/m)  A. 3 m/s  B. 48 m/s  C. 0.75 N  D. 48 N

13. GRAViTY  The pull of one body of mass on another.

14. What two factors change gravitational force?  A. Speed and direction.  B. Mass and distance.  C. Mass and velocity.  D. Speed and momentum.

15. Weight is a force that depends on gravity and  A. mass.  B. acceleration.  C. friction.  D. force.

16. Acceleration due to gravity  All objects fall at the same rate, regardless of their mass or weight  The acceleration due to gravity on earth is about 9.8 m/sec 2.  This value will change with elevation and location on earth.

17. Terminal Velocity  After a period of free fall, the force of gravity will be canceled by the force of air friction and objects will travel at a constant velocity

18. The forces acting on a falling leaf are gravity and air resistance. If the leaf falls at a constant rate,  A. forces are balanced.  B. forces are unbalanced.  C. the world will end.  D. a leaf never falls at a constant rate.

19. Newton’s First Law of motion  An object at rest will remain at rest and an object in motion will remain in motion unless acted upon by an outside force.  Often referred to as the Law of Inertia. (the property of matter that resists any change in motion)

20. The property of matter that resists changes in motion is called  A. centripetal motion.  B. friction.  C. inertia.  D. projectile motion.

21. Inertia is related to  A. speed.  B. weight.  C. mass.  D. motion.

22. An orange might roll off your cafeteria tray when you stop suddenly because of  A. the balanced forces acting on the orange.  B. the friction forces acting on the orange.  C. the centripetal force acting on the orange.  D. the orange’s inertia.

23. Newton’s Second Law of Motion  The force of a moving object is directly proportional to the object’s mass and acceleration.  The most important of Newton’s laws.

24. According to Newton’s second law, the acceleration equals the net force divided by the object’s  A. mass.  B. velocity.  C. momentum.  D. weight.

25. Weight and Mass  MASS  The measure of inertia of an object.  The amount of matter in an object  Stays constant with changes in location  A scalar  WEIGHT  A measure of the force of gravity acting on an object.  Measured in newtons.  Changes with changes in location.  A vector

26. Your weight equals your  A. mass  B. mass divided by the net force acting on it.  C. mass times acceleration due to gravity.  D. mass times your speed.

27. Why is your weight less on the moon?  A. Mass changes on the moon.  B. Gravity is less on the moon.  C. Gravity is greater on the moon.  D. Weight never changes, only mass changes.

28. Newton’s Third Law of Motion  For every action there is an equal and opposite reaction, or  All forces occur in pairs  examples:

29. Newton’s third law of motion describes  A. action and reaction forces.  B. centripetal forces.  C. balanced forces.  D. net force.

30. When one object exerts a force on another,  A. the objects will always move as a result of the interaction.  B. an equal and opposite force is exerted back on it by the other object.  C. the objects will never move due to the forces cancelling each other out.  D. one object will always exert a greater force on the other object.

31. Momentum  All moving objects have momentum.  How hard is it to stop and object.  It is the product of an object’s mass and velocity.  the mass matters  the speed matters  p = mv

32. What is the momentum of a truck at rest?  A. Zero  B. Equal to the mass.  C. Equal to the weight.  D. Trucks do not need to rest.

33. If a golf ball and marble are rolling at the same speed, which has a greater momentum?  A. Golf ball  B. Marble  C. They have the same.  D. I lost my marbles a long time ago!

34. The product of an object’s mass and velocity is its  A. centripetal force.  B. net force.  C. momentum.  D. weight.  P = mv