Chapter 7 Ai

Question 1

What is the equation for work?

Answer 1

W = Fd

Work involves force and distance.

Question 2

What unit is used to measure work?

Answer 2

Newton-meter (Nm) or joule (J).

Question 3

If you push against a stationary wall, do you do work on the wall?

Answer 3

No.

Question 4

How much work is done in lifting a barbell that is twice as heavy the same distance?

Answer 4

Twice as much.

Question 5

What is power?

Answer 5

Measure of how fast work is done.

Question 6

What is the unit of power?

Answer 6

Joule per second, called the watt.

Question 7

What is mechanical energy?

Answer 7

Energy due to position or to motion, or both.

Question 8

What are the two forms of mechanical energy?

Answer 8

• Potential energy
• Kinetic energy

Question 9

What is potential energy?

Answer 9

Stored energy held in readiness with a potential for doing work.

Question 10

What is gravitational potential energy?

Answer 10

Potential energy due to elevated position, calculated as mgh.

Question 11

What is kinetic energy?

Answer 11

Energy of motion, calculated as 1/2 x mass x speed².

Question 12

What theorem relates work to kinetic energy?

Answer 12

Work-Energy Theorem.

Question 13

What does the Work-Energy Theorem state?

Answer 13

Gain or reduction of energy is the result of work.

Question 14

What is the law of conservation of energy?

Answer 14

Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.

Question 15

What is a machine?

Answer 15

A device for multiplying forces or changing the direction of forces.

Question 16

What is the simplest machine?

Answer 16

Lever.

Question 17

What does efficiency measure?

Answer 17

Percentage of work put into a machine that is converted into useful work output.

Question 18

What is recycled energy?

Answer 18

Re-employment of energy that otherwise would be wasted.

Question 19

What do cells in our body feed on to release energy?

Answer 19

Hydrocarbons that react with oxygen.

Question 20

What is an example of energy from the Sun?

Answer 20

Sunlight evaporates water, which falls as rain, flowing into rivers and into generator turbines.

Question 21

What is a fuel cell?

Answer 21

A device that produces electric current from hydrogen and oxygen.

Question 22

What is nuclear power stored in?

Answer 22

Uranium and plutonium.

Question 23

True or False: Kinetic energy can be canceled.

Answer 23

False.

Question 24

Fill in the blank: Potential energy is equal to _______.

Answer 24

mass x acceleration due to gravity x height (mgh).

Question 25

What happens to kinetic energy if the speed of an object is doubled?

Answer 25

Kinetic energy is quadrupled.

Question 26

What happens to the stopping distance if the initial speed of a car is doubled?

Answer 26

Stopping distance is four times greater.

Question 27

What percentage of energy input will be wasted in a machine that is 30% efficient?

Answer 27

70%.

Question 28

What is the relationship between momentum and kinetic energy?

Answer 28

Both are properties of moving things; momentum is a vector quantity and kinetic energy is a scalar quantity.