Work, Energy, and Power

Question 0

What is work?

Answer 0

• When a force acting on an object causes a displacement of the object
• transfer of energy

Question 1

What is the unit of work?

Answer 1

Joule (Newton/meter)

Question 2

What is the difference between negative and positive work?

Answer 2

Positive- force (parallel component) exerted parallel to displacement

Negative- force exerted (parallel component) not the same direction as d, hinders displacement

Question 3

What is potential energy?

Answer 3

• Stored energy

- the amount of energy an object can potentially have

Question 4

Where does the energy from work go?

Answer 4

• moves object (break from friction)
• heat block and atmosphere
• creates sound

Question 5

What is gravitational potential energy?

Answer 5

-Energy stored in an object as a result of its height

Question 6

What is the relationship between gravitational potential energy and height?

Answer 6

The higher an object is, the more potential energy it has

Question 7

What is gravitational potential energy dependent on?

Answer 7

Mass and height of object

Question 8

What must be assigned to determine the gravitational potential energy of an object?

Answer 8

A zero height position or reference level

Question 9

What is elastic potential energy?

Answer 9

Energy stored in elastic materials (like spring) as a result of a stretching or compression

Question 10

What does kx represent?

Answer 10

The force someone applies to a spring

Question 11

What does -kx represent?

Answer 11

The force the spring applies to the object which is also applying a force on the spring

Question 12

What does the law of conservation of energy state?

Answer 12

• The total amount of energy in the universe never changes.

- Energy is conserved; it can’t be created or destroyed, only transferred from one form to another.

Question 13

Is work scalar or vector?

Answer 13

Scalar

Question 14

Is spring force conservative?

Answer 14

Yes; you can recover the force exerted on the spring by releasing the spring

Question 15

What does the conservation of mechanical energy state?

Answer 15

In any ISOLATED SYSTEM of objects interacting only through CONSERVATIVE FORCES, the total mechanical energy of the system remains the SAME at all times.

Question 16

What is power?

Answer 16

Work/rate of energy transfer with time (average power)

Question 17

What is kinetic energy?

Answer 17

Energy of motion

Question 18

What is mechanical energy?

Answer 18

• the energy acquired by objects when work is done on it

- can be either kinetic or mechanical

Question 19

Why was the joule names after James Prescott Joule?

Answer 19

James Prescott Joule was credited for discovering the law of conservation of energy

Question 20

Who invented the joule?

Answer 20

James Prescott Joule

Question 21

Where do human beings get energy to move?

Answer 21

Food

Question 23

What is the unit for power?

Answer 23

• The rate of energy transfer over time

- the amount of work done over time

Question 24

What is the speed needed for a projectile to leave the earth’s atmosphere?

Answer 24

about 11 km/s

Question 25

What the equation for stable equilibrium?

Answer 25

-change in potential energy/change in displacement

Question 26

What are conservative forces?

Answer 26

• forces that can be easily recovered

- if the work a force does moving an object between two objects is the same no matter what path is taken

Question 27

What are nonconservative forces?

Answer 27

forces that cannot be easily recovered

Question 28

What does the work-energy theorem relate?

Answer 28

work with energy (W= change in kinetic energy)