Newton’s Laws and Fun Forces Review
Part I: Multiple Choice
1. The law of inertia states that an object ___.
a) at rest will remain at rest unless acted on by an outside force.
b) will continue moving at the same velocity unless an outside force acts on it.
c) will continue moving in a straight line unless an outside force acts on it.
d) that is not moving will never move unless a force acts on it.
e) All of the above
2. The law of inertia applies to ___.
a) moving objects.
b) objects at rest.
c) both moving and nonmoving objects.
3. After a cannon ball is fired into frictionless space, the amount of force needed to keep it going equals ___.
a) twice the force with which it was fired.
d) one quarter of the force with which it was fired.
b) one half the force with which it was fired.
e) the same amount of force with which it was fired.
c) zero, since no force is necessary to keep it moving.
4. One object has twice as much mass as another object. The first object also has twice as much ___.
a) inertia
d) acceleration
b) velocity
e) all of the answers are correct
c) gravitational acceleration
5. Compared to its weight on earth, a 10-kg object on the moon will weigh ___.
a) less.
b) more.
c) the same amount.
6. Compared to its mass on earth, the mass of a 10-kg object on the moon is ___.
a) less.
b) more.
c) the same.
7. An object following a straight-line path at constant speed ___.
a) has zero acceleration.
d) has a net force acting on it in the direction of motion.
b) must be moving in a vacuum.
e) There is no correct answer
c) has an unbalanced force acting on it.
8. A 10-N force and a 30-N force act on an object in opposite directions. What is the net force on the
object?
a) 40 N
b) 30 N
c) 20 N
d) 10 N
e) none of the above
9. Equilibrium occurs when ___.
a) all the forces acting on an object are balanced.
b) the sum of the +x forces on an object equals the sum of the –x forces.
c) the sum of the upward forces equals the sum of the downward forces.
d) the net force on the object is zero.
e) All of the above.
10. Which has more mass, a kilogram of feathers or a kilogram of iron?
a) the feathers
b) the iron
c) neither, both have the same mass
11. Whenever an object exerts a force on another object, the second object exerts a force of the same
magnitude, but in the opposite direction to that of the first object.
a) always true
b) sometimes true
c) always false
12. Forces always occur ___.
a) by themselves.
b) as single quantities
c) in pairs
d) in triplets
13. A student hits a nail with a hammer. During the collision, there is a force ___.
a) on the hammer but not on the nail
b) on the nail but not on the hammer
c) on the nail and also on the hammer
14. A person is attracted towards the center of the earth by a 500-N gravitational force. The force with
which the earth is attracted toward the person is ___.
a) very very small
b) very very large
c) 500 N
15. A car traveling at 100 km/hr strikes a hapless bug and splatters it. The force of impact is greater on
the ___.
a) bug.
B) car.
c) is the same for both.
16. A sheet of paper can be withdrawn from under a container of milk without falling over if the paper is
jerked quickly. The reason this can be done is that ___.
a) the milk carton has no acceleration.
c) the gravitational field pulls on the milk carton.
b) there is an action-reaction pair operating
d) the milk has inertia.
17. The force of friction on a sliding object is 10 N. The applied force needed to maintain a constant
velocity is ___.
a) more than 10 N
b) less than 10 N
c) 10 N
18. A 2 kg block is pulled horizontally with a constant speed across the floor with a force of 10 N.
Determine the magnitude of the frictional force acting on the block.
a) 0 N
b) 5 N
c) 10 N
d) 20 N
e) can not be determined
19. A ball is left in the middle of the bed of a truck. If the truck accelerates forward the ball will ___.
a) hit the cab of the truck due to Newton’s third law.
b) hit the cab of the truck due to Newton’s first law.
c) hit the tailgate of the truck due to Newton’s third law.
d) hit the tailgate of the truck due to Newton’s first law.
II. Place a T (true) or F (false) in each blank.
T 20. If an object is in physical equilibrium, the net force on the object must be zero.
F 21. If the net force on an object is zero, it must be at rest.
F 22. Any object with zero acceleration must have a constant velocity.
F23. Any object with zero acceleration must be at rest.
T 24. If the net force on an object is zero, the velocity of the object will remain constant
F 25. An object in constant motion always requires a constant force.
F 26. An object at rest must not have any forces acting on it.
F27. The normal force is a pushing force by a surface to the object and is parallel to the surface.
T 28. An object with all forces balanced must have an acceleration of zero.
T 29. An object with zero acceleration must be in static equilibrium.
F30. A large truck collides with a small economy car. The smaller car experiences a greater force than the
truck.
T31. A girl kicks a soccer ball applying a force to the ball, the ball applies an equal force in the opposite
direction to the girl.
F32. A bowling ball, moving at a velocity of 1 m/s, has less inertia than a ping-pong ball moving at a velocity
of 10 m/s.
III. Short Answer
33. In any situation where an object is supported by a flat surface, how would decrease the normal
force exerted on the object?
You would apply an additional force in the same direction in the normal force.
34. Explain what it means to “charge” an object.
When cause an object to be negatively charged you are transferring electrons to that object. If you
are causing an object to be positively charged then you are transferring electrons away from that
object.
35. Explain how the particles will move in each of the following situations.
1
M1
M2
M3
+q2
2
+q1
+q3
In situation one, the force between the particles is gravitational force. Gravitational force is always
attractive so the objects will all exert an equal amount of force on each other. When this happens, all
the particles will move straight towards the middle of the triangle.
In the second situation, the force between the particles is repulsive because they are all like charges.
These charges will move straight out from the middle of the triangle away from each other because
they all have the same charge and they are all acting equally on each other.
36. Explain how Fe would change in each of the following situations: Plug the numbers into the actual
equation.
Increase q1 by 4 and cut r in half: k=1, q2=1, q1=4, r=1/2
(1)(4)(1)
(1/2)2
(1)(4)(1)(4) = 16x greater
Cut each charge in half and increase d by 4: k=1, q2=1/2, q1=1/2, r=4
(1)(1/2)(1/2)
(4)2
(1) _ = 1/64 or 64x less
(4)(16)