AnswersTX-Physics AUnit Test

Unit Test — Unit test Answers

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1
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The free-body diagrams of four objects are shown.

Question illustration
A
W
B
X
C
Y
D
Z
2
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Newton’s third law of motion says that for every action there is a(n) and opposite reaction.

Answer not available
3

A sports car and a minivan run out of gas and are pushed to the side of the road. Which is easier to push, and why?

A
the minivan, because it has more mass and therefore more inertia
B
the minivan, because it has less mass and therefore less inertia
C
the sports car, because it has more mass and therefore more inertia
D
the sports car, because it has less mass and therefore less inertia
4

According to Newton’s first law of motion, what will an object in motion do when no external force acts on it?

A
come to a stop
B
move at the same velocity
C
speed up
D
change direction
5

The gravitational force between two objects is 2000 N. The mass of each object is reduced to one-third of its original mass.

A
The distance must be one-ninth the original distance.
B
The distance must be one-third the original distance.
C
The distance must be three times greater.
D
The distance must be nine times greater.
7

The image shows a model of the gravitational field around Earth.

Question illustration
A
The field exerts an attractive force only outside of the ring of arrows that point toward Earth’s surface.
B
The field exerts an attractive force only within the ring of arrows that point toward Earth’s surface.
C
The strength of the field increases as you get farther from Earth, as shown by the larger spaces between the circles.
D
The strength of the field increases as you get closer to Earth, as shown by the smaller spaces between the circles.
8

A probe orbiting Venus exerts a gravitational force of 2.58 × 103 N on Venus. Venus has a mass of 4.87 × 1024 kg. The mass of the probe is 655 kilograms. The gravitational constant is 6.67 × 10-11 N*m2/kg2.To three significant digits, the probe is × 106 m from the center of Venus.

Answer not available
9

Which statements describe an object in motion that has no external force acting on it? Check all that apply.It accelerates and speeds up.It moves at a constant speed.It decelerates and slows down.It changes direction.It moves in the same direction.

A
It accelerates and speeds up.
B
It moves at a constant speed.
C
It decelerates and slows down.
D
It changes direction.
E
It moves in the same direction.
10

A box is being pulled to the right. What is the direction of the gravitational force?

A
up
B
down
C
right
D
left
11

The gravitational force between two objects is 45,000 N. What will be the gravitational force between the two objects if the distance between the objects is reduced by one-half?

A
11,250 N
B
22,500 N
C
90,000 N
D
180,000 N
12

Which object is in static equilibrium?

A
a rolling ball that has a net force acting on it
B
a cruising car that has no net force acting on it
C
a book that has no net force acting on it and is sitting on a table
D
a vase that has a net force acting on it and is sitting on a shelf
13

Which is an action/reaction force pair? Check all that apply.Earth pulls on a book, and the book pushes against a shelf.A hockey stick hits a puck, and the puck pushes against the stick. A pencil pushes against a piece of paper, and the paper pushes against the desk.A finger pulls on a rubber band, and the rubber band pushes against the finger.A dog pulls on a leash, and the owner pulls back on the leash.

A
Earth pulls on a book, and the book pushes against a shelf.
B
A hockey stick hits a puck, and the puck pushes against the stick.
C
A pencil pushes against a piece of paper, and the paper pushes against the desk.
D
A finger pulls on a rubber band, and the rubber band pushes against the finger.
E
A dog pulls on a leash, and the owner pulls back on the leash.
14

A car is moving east along a straight, level road at a constant velocity. Which forces form an action/reaction force pair?

A
the force of the tires against the road and the force of the road on the tires
B
the weight of the car and the force of the road pushing up on the car
C
the force of the engine on the car and the force due to friction on the car
D
the normal force on the car and the force of the car pulling on Earth
15

Which changes would result in a decrease in the gravitational force between two objects? Check all that apply.increasing the distance between the objectsdecreasing the distance between the objectsincreasing the mass of one of the objectsincreasing the mass of both objectsdecreasing the mass of one of the objectsdecreasing the mass of both objects

A
increasing the distance between the objects
B
decreasing the distance between the objects
C
increasing the mass of one of the objects
D
increasing the mass of both objects
E
decreasing the mass of one of the objects
F
decreasing the mass of both objects
16

John pushes Hector on a plastic toboggan.The free-body diagram is shown.

Question illustration
A
245 N
B
735 N
C
490 N
D
980 N
17

JouleNewtonWatt

A
Joule
B
Newton
C
Watt
18

A rocket experiences a constant force even as the amount of fuel in its fuel tanks decreases. What happens to the acceleration of the rocket as it runs out of fuel?

A
The acceleration decreases because the mass increases.
B
The acceleration increases because the mass increases.
C
The acceleration decreases because the mass decreases.
D
The acceleration increases because the mass decreases.
19

2.863.244.165.44

A
2.86
B
3.24
C
4.16
D
5.44
20

Which situation is contrary to Newton’s first law of motion?

A
An object at rest begins to move when an external force is applied.
B
A moving object has a constant velocity under the influence of balanced forces.
C
An object at rest stays at rest as long as unbalanced forces act on it.
D
A moving object slows down when an external force is applied.
21

Juan draws a free-body diagram of an object that is in dynamic equilibrium moving to the left.

Question illustration
A
X: 45 NY: –45 N
B
X: –45 NY: 30 N
C
X: 30 NY: –45 N
D
X: 30 NY: –30 N

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