# Physics Test 3 Multiple Choice

## 20 terms

### (b) will not change motion unless an external net force is acting on it

The Law of Inertia (Newton's First Law) states that an object
(a) at rest will never move
(b) will not change motion unless an external net force is acting on it
(c) will slow down unless an external force is acting on it
(d) all the above (e) none

### (d) all the above

The acceleration produced by a net force on an object (Newton's 2nd Law) is
(a) in the same direction as the net force
(b) directly proportional to the magnitude of the net force
(c) inversely proportional to the mass of the object
(d) all the above (e) none

### (c) the object's velocity must be constant

What must be true in order for an object to be in equilibrium?
(a) the object's velocity must be changing
(b) the object must be at rest
(c) the object's velocity must be constant
(d) the object must be moving

### (a) is 10 times as much as the force on the book

A brick with a mass of 10 kg and a book with a mass of 1 kg are dropped in a vacuum (no air friction) near the Earth's surface. The force of gravity on the 10 kg brick
(a) is 10 times as much as the force on the book
(b) is the same as on the book
(c) is one-tenth as much as the force on the book
(d) is zero

### (a) opposite the object's motion

Sliding/kinetic energy is a force that always acts
(a) opposite the object's motion
(b) in the same direction as the object's motion
(c) perpendicular to the object's motion
(d) all the above (e) none

### (c) the ball pushing on the hockey stick

A field hockey player hits the ball down the field. Consider the action force to be the stick pushing the ball. The reaction force would be
(a) the ball accelerating towards the goal
(b) the hockey stick pushing on the player
(c) the ball pushing on the hockey stick
(d) gravity pulling down on the ball (e) none

### (c) 10 N

Suppose the force of friction on a sliding object is 10 N. The push force needed to maintain a constant velocity is
(a) less than 10 N (b) more than 10 N (c) 10 N
(d) depends on the mass of the object
(e) depends on object's speed

### (e) 20 N

A ball has a mass of 2 kg. When in free fall, the net force on the ball is about
(a) 0 N (b) 0.2 N (c) 2 N (d) 10 N (e) 20 N

### (a) more than half your weight

If you hang from two pieces of vertical rope, the tension in each rope is half your weight. If the lines are not vertical, but are at equal angles from the vertical the tension in each piece of rope is
(a) more than half your weight
(b) less than half your weight

### (a) 0 m/s/s

When an object reaches terminal velocity, its acceleration is
(a) 0 m/s/s (b) 10 m/s/s upward (c) 10 m/s/s downward
(d) depends on its mass

### (a) less than 10 N

If you push on a book with a force of 10 N and the book accelerates (increases its velocity) while you are pushing it, how much is in the friction force?
(a) less than 10 N (b) 10 N (c) more than 10 N
(d) depends on the coefficient of friction
(e) depends on the normal force

### (b) 1 m/s/s

Suppose that a cart has a net force that is accelerating it at 3 m/s/s. More mass is added to the cart and now the total mass is 3 times the original amount. If the same net force is applied, the acceleration will be
(a) 0 m/s/s (b) 1 m/s/s (c) 3 m/s/s (d) 9 m/s/s (e) 10 m/s/s

### (c) neither, their masses are equal

Which has more mass, a kilogram of feathers or a kilogram of iron?
(a) feathers (b) iron (c) neither, their masses are equal

### (e) 10 N, down

A 15 N object is falling and encounters 5 N of air resistance. The net force on the object is
(a) 0 N (b) 20 N, down (c) 20 N, up (d) 10 N, up (e) 10 N, down

### (b) equal to 500 N

A person is attracted towards the earth by a 500 N gravitational force. The force with which the earth is attracted toward the person is
(a) much smaller than 500 N
(b) equal to 500 N (c) much larger than 500 N
(d) impossible, the earth cannot be attracted to a person

### (c) the ball with the larger force also has the larger mass

The reason a tennis ball and a solid steel ball will accelerate at the same rate, in a vacuum (no air friction), is
(a) the size of the force acting on them is the same
(b) they have the same mass
(c) the ball with the larger force also has the larger mass
(d) the ball with the larger force also has a smaller mass

### (a) it is equal to 0 N (like free fall)

An object is falling near the surface of the earth and has an acceleration of 10 m/s/s downwards. What can be said about the magnitude of the force of the air resistance?
(a) it is equal to 0 N (like free fall)
(b) it is less than the weight of the object
(c) it is equal to the weight of the object
(d) it is more than the weight of the object

### (a) 0 N

A ball has a mass of 2 kg. When the ball is held at rest above your head, the net force is about
(a) 0 N (b) 2 N (c) 5 N (d) 10 N (e) 20 N

### (c) greater than 0 N downward

Before an object reaches terminal velocity, the net force acting on it is
(a) 0 N (b) greater than 0 N upwards
(c) greater than 0 N downward (d) could be b or c
(e) can't tell, you need the mass

### (c) 100 N

You stand on a scale and find that you weight 400 N. You find three other scales, and place them so you have a hand or foot on each scale (push-up style). Each scale would indicate a weight of about
(a) 400 N (b) 200 N (c) 100 N (d) 50 N (e) 25 N