AnswersPhysics IWork and Power

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1
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In which scenario is an animal doing work? Choose three correct answers.

A
A horse pulls a wagon along a road.
B
A goat butts its head against the barn wall.
C
A dog rubs his back against a large tree.
D
A bird flies a worm from the ground to its nest in a tree.
E
A cat lifts up her kitten by its neck.
2
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How do the units of work and power compare?

A
The unit for work is a joule. The unit for power is a watt, which is a joule-second.
B
The unit for work is a watt. The unit for power is a joule, which is a watt per second.
C
The unit for work is a watt. The unit for power is a joule, which is a watt-second.
D
The unit for work is a joule. The unit for power is a watt, which is a joule per second.
3

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

A
The faster the job is done, the greater the power.
B
The less work is done, the more power is needed.
C
The longer the job takes, the more work is done.
D
The greater the power applied, the more work is done.
4

How is power calculated?

A
divide work by time
B
multiply work and time
C
multiply force and displacement
D
divide force by displacement
5

Lester prepares to lift a heavy sack of flour into a customer’s shopping cart. During which part of the action does Lester do work?

A
when he holds the sack against his chest
B
as he lets go of the sack and it falls onto a cart
C
when he applies force to the sack before lifting it
D
as he lifts the sack to his chest from the floor
6

Hiro walks up a flight of stairs in his apartment building. Later in the day, he runs up the same flight of stairs. Which statement about work and power describes Hiro’s actions?

A
He had more power walking than running.
B
He had more power running than walking.
C
He did more work running than walking.
D
He did more work walking than running.
7

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

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

Which statement about work and power correctly describes an automobile race?

A
The car that finishes last has the lowest power.
B
The car with the greatest power travels the greatest distance.
C
The cars do different amounts of work depending on their power.
D
The cars do different amounts of work depending on how fast they finish.
9

Hiro walks up a flight of stairs in his apartment building. Later in the day, he runs up the same flight of stairs. Which statement about work and power describes Hiro’s actions?

A
He did more work running than walking.
B
He did more work walking than running.
C
He had more power running than walking.
D
He had more power walking than running.
10

In which scenario is the least amount of work done on a crate?

A
A force of 120 N moves it 25 m.
B
A force of 125 N moves it 27 m.
C
A force of 130 N moves it 22 m.
D
A force of 115 N moves it 26 m.

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