AnswersCrowley Credit Recovery Physics AUnit Test

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Lenny wrote the steps he used to find the mass of an object with 400 J of energy moving at a velocity of 8 m/s.1. Find the square of 8 m/s, which is 64 m2/s2. 2. Divide kinetic energy, 400 J, by 64 m2/s2, which is 6.25 J per m2/s2.3. Divide 6.25 J per m2/s2 by 2 to get a mass of 3.125 kg.

A
In Step 1, he should have found the square root of 400 J instead of squaring 8 m/s.
B
In Step 1, he should have multiplied 8 m/s by 2 instead of squaring it.
C
In Step 2, he should have divided 64 m2/s2 by 400 J instead of dividing 400 J by 64 m2/s2.
D
In Step 3, he should have multiplied 6.25 J per m2/s2 by 2 instead of dividing it by 2.
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Which best identifies the requirements for work to be performed?

A
an object that has a force acting on it
B
an object that is moving and has no net force
C
a force acting on a motionless object
D
a force that moves an object
4

Examine the scenarios.Scenario W: A force of 75 N moves a box 15 m.Scenario X: A force of 100 N moves a box 12 m.Scenario Y: A force of 50 N moves a box 20 m.Scenario Z: A force of 25 N moves a box 45 m.

A
W and X
B
W and Z
C
X and Y
D
Y and Z
5

What is the potential energy of a spring that is compressed 0.65 m by a 25 kg block if the spring constant is 95 N/m?

A
1.6 J
B
7.9 J
C
15 J
D
20 J
6

A force of 75 N at an angle of 15° to the direction of motion moves a chair 3 m. Which change would result in more work being done on the chair?

A
using 60 N of force
B
moving the chair 2 m
C
increasing the angle to 20°
D
decreasing the angle to 10°
8

Every spring has an equilibrium position. Which statements describe a spring at its equilibrium position? Check all that apply.

A
The spring constant is zero.
B
The elastic potential energy is at a maximum.
C
The elastic potential energy is zero.
D
The displacement of the spring is at a maximum.
E
The net force acting on the spring is zero.
9

How does the work needed to lift an object and the gravitational potential energy of the object compare?

A
They are equal.
B
The work is greater.
C
The work is less.
D
The comparison depends on the height.
10

Which best summarizes a concept related to the work-energy theorem?

A
When work is positive, the environment does work on an object.
B
When work is negative, the environment does work on an object.
C
When work is positive, the kinetic energy in a system remains constant.
D
When work is negative, the kinetic energy in a system remains constant.
11

What is the basis for analyzing an energy transfer diagram?

A
The mechanical energy input and output must be equal.
B
Heat must always be the largest output.
C
The sum of all outputs must equal the input.
D
Electrical energy is an input but not an output.
12

[BLANK]

A
kinetic
B
potential
C
gravitational
D
work
13

What term is used to describe a system that loses energy to objects that are not part of the system?

A
raised
B
low
C
open
D
closed
14

What does the law of conservation of energy state about energy in a closed system?

A
Energy cannot be created or destroyed.
B
Energy can be created but not destroyed.
C
Energy can be destroyed but not created.
D
Energy can be either destroyed or created.
15

In which scenario is an animal doing work? Check all that apply.

A
A cat lifts up her kitten by its neck.
B
A dog rubs his back against a large tree.
C
A bird flies a worm from the ground to its nest in a tree.
D
A goat butts its head against the barn wall.
E
A horse pulls a wagon along a road.
16

Natalia lifts a bag of groceries 0.50 m by exerting a force of 36 N. How much work did she do on the bag?

A
0 J
B
18 J
C
36 J
D
72 J
17

A load of bricks is lifted to the second floor of a building. How do work and power relate to this job?

A
The longer the job takes, the more work is done.
B
The faster the job is done, the greater the power.
C
The greater the power applied, the more work is done.
D
The less work is done, the more power is needed.
18

In which scenario is gravitational potential energy present?

A
A rabbit looks out of a hole in the ground.
B
A squirrel runs up the trunk of a tree.
C
A deer runs across a grassy field.
D
A cat pins a mouse to the ground.
19

A loudspeaker converts electrical energy into the kinetic energy of the speaker. This kinetic energy is transferred to air, and the motion of the air is the sound that people hear.

Question illustration
A
5 J
B
15 J
C
80 J
D
100 J
21

Which formula can be used to find velocity if kinetic energy and mass are known?

A
v =
Option A
B
v =
Option B
C
v =
Option C
D
v =
Option D
22

When an object is not in motion, it can still have a form of energy. What form of energy does an object have due to its distance from Earth?

A
kinetic energy
B
thermal energy
C
gravitational potential energy
D
electrical potential energy
23

A ball has 116.62 J of gravitational potential energy at a height of 85 m. What is the mass of the ball?

A
0.14 kg
B
0.37 kg
C
11.9 kg
D
21.82 kg

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