Module 8 review questions

Question 1

A secret agent is locked in a room. He pushed and pushes against the door but cannot open it. Finally, he falls on the floor exhausted. Has he done any work on the door? Why or why not?

Answer 1

The secret agent has done no work, because no displacement has occurred.

Question 2

Which of the following are legitimate units for energy?
J/s, inch x lbs, kg x m/sec^2, Newton x m^2, Newton x km

Answer 2

Any unit that has a force unit times a distance unit is a legitimate energy unit. inch x lbs and Newton x km

Question 3

Is the energy in a full tank of gasoline potential or kinetic energy?

Answer 3

potential

Question 4

Is the energy in a car traveling down the road potential or kinetic energy?

Answer 4

kinetic

Question 5

Is the energy in electricity moving through a wire potential or kinetic energy?

Answer 5

kinetic

Question 6

Is the energy in a ripe apple hanging in a tree potential or kinetic energy?

Answer 6

potential

Question 7

A rock is at rest on the top of a cliff. Suddenly, a small breeze pushes it off the cliff. Where is the potential energy the greatest? Where is the kinetic energy the greatest? At what point in its fall is the kinetic energy equal to the potential energy?

Answer 7

Potential energy is the greatest at the top of the cliff where there is the most height.
Kinetic energy is the greatest right before it hits the ground when all of the potential energy has been converted to kinetic energy
Potential and kinetic energy are equal halfway down.

Question 8

Two boxes slide down a level sidewalk. The first is heavier than the second; other than that they are identical. If they start with equal speeds which will slide the farthest?

Answer 8

They slide the same distance. The frictional force is greater for the heavier box, but it also has more kinetic energy, cancelling it out.

Question 9

What is the difference between energy and power?

Answer 9

Energy is the ability to do work, while power is the measure of how much work was done in a specific time interval.

Question 10

Two light bulbs are in two different lamps. Although they are both the same type of light bulb, the first is significantly dimmer than the second. Which light bulb consumes more power?

Answer 10

The second.

Question 11

Which of the following are legitimate units for power?
kiloWatts, N/sec, J x sec, kiloJoules/year

Answer 11

Any energy unit divided by a time unit is a legitimate power unit. kiloJoules/year and kiloWatts, becuase Watt is a power unit.