Work, Energy & Power

Question 1

What is work done?

Answer 1

The amount of energy transferred when an external force causes an object to move a certain distance

Question 2

What is the work done equation of if the force is parallel to the objects displacement?

Answer 2

W = Fx

W = work done J
F = force applied N
x = displacement m

Question 3

What is 1 joule?

Answer 3

The energy transferred to (or work done on) an object when a force of 1 N acts on the object parallel to its motion through a distance of 1 m

Question 4

What is the SI unit for a joule?

Answer 4

kg m^2 s^-2

Question 5

What is the work done equation if the force is at an angle in comparison to the motion (horizontal) ?

Answer 5

W = Fx cos θ

Question 6

What is the work done equation if the force is at an angle in comparison to the motion (vertical) ?

Answer 6

W = Fx sin θ

Question 7

What is the principle of conservation of energy?

Answer 7

Energy cannot be created or destroyed, it can only be transferred from one form to another

Question 8

What is kinetic energy?

Answer 8

The energy of a moving object

Question 9

What is gravitational potential energy?

Answer 9

The energy stored in a mass due to its position in a gravitational field

Question 10

What is elastic energy?

Answer 10

The energy of a stretched spring or elastic band

Question 11

What is chemical energy?

Answer 11

The energy contained in a chemical substance

Question 12

What is nuclear energy?

Answer 12

The energy contained within the nucleus of an atom

Question 13

What is internal energy?

Answer 13

The energy something has due to its temperature

Question 14

What are the energy transfers?

Answer 14

• Kinetic
• Thermal
• Sound
• Electrical
• Light

Question 15

What are the energy stores?

Answer 15

• Elastic
• Gravitational potential
• Chemical
• Nuclear

Question 16

What is energy dissipation?

Answer 16

It describes the ways in which energy is wasted ; when energy is transferred from one form to another, not all the energy will end up in the desired form. Any energy not transferred to the useful store is wasted

Question 17

What are the energy transfers for a falling object?

Answer 17

Gravitational potential energy —> kinetic energy

Question 18

What are the energy transfers for a battery (connected to a bulb)?

Answer 18

Chemical energy —> electrical energy —> light energy

Question 19

What are the energy transfers for a horizontal mass on a string?

Answer 19

Elastic potential energy —> kinetic energy

Question 20

What does loss in GPE equal?

Answer 20

Gain in kinetic energy

Question 21

What is the transfer of energy equal to?

Answer 21

Work done

Question 22

The faster an object is moving, the _______ its kinetic energy

Answer 22

Greater

Question 23

What is the kinetic energy equation?

Answer 23

KE = 1/2 mv^2

Question 24

How do you derive the KE equation?

Answer 24

Question 25

What happens when a mass is lifted in a gravitational field?

Answer 25

It gains GPE

Question 26

What is the GPE equation?

Answer 26

GPE = mgh

m = mass kg
g = gravitational field strength, 9.81 Nkg^-1
h = change in height

Question 27

How do you derived the GPE equation?

Answer 27

F = mg and x = Δh
W = Fx
so W = mgh

Question 28

What has to be taken as negligible if loss in potential energies equals gain in kinetic energy?

Answer 28

Drag forces

Question 29

What is power?

Answer 29

The rate of energy transfer

Question 30

What are the equations for power?

Answer 30

P = E / t

P = Fv

E = work done J
t = time s
P = power W
F = force N
v = velocity ms^-1

Question 31

What is efficiency?

Answer 31

The ratio of useful power output from a system to its total power input

Question 32

What is the efficiency equation?

Answer 32

Useful power output / useful power input x 100%