Module 3.3 - Work, Energy and Power

Question 1

What is work done?

Answer 1

The energy transferred

Question 2

How do you work out work done, w?

Answer 2

Work done = force x distance

W = f x d

Question 3

How do you work out work done when a mass is given?

Answer 3

W = mg x d

Question 4

How do you work out work done at an angle?

Answer 4

W = f x cos(theta) x d

Question 5

At what angle is there no work done and why ?

Answer 5

90˚ as cos(90) = 0

Question 6

What is a closed system?

Answer 6

Any system where every transfer of energy is accounted for

Question 7

What is a joule?

Answer 7

> Unit of energy - J
Equivalent to one Nm
One joule of work is transferred when a force of 1N causes an object to move a distance of 1m

Question 8

What is the principle of conservation of energy?

Answer 8

States that the total energy of a closed system remains CONSTANT. Energy cannot leave or enter the system.

Question 9

What are the two forms of energy?

Answer 9

> Transfer

> Conservation

Question 10

What are the nine types of energy stores?

Answer 10

> Kinetic
> Thermal 
> Nuclear 
> Chemical 
> Internal 
> Gravitational
> Elastic
> Electrostatic 
> Magnetic

Question 11

Where are kinetic energy stores found?

Answer 11

In a moving object

Question 12

Where are thermal energy stores found?

Answer 12

In a warm object

Question 13

Where are gravitational energy stores found?

Answer 13

In a lifted object

Question 14

Where are elastic energy stores found?

Answer 14

e.g. stretched or compressed spring

Question 15

Where are chemical energy stores found?

Answer 15

Between atoms and molecules that could react

Question 16

Where are magnetic energy stores found?

Answer 16

In two separate magnets that are attracting or repelling

Question 17

Where are electrostatic energy stores found?

Answer 17

In two separated electric charges that

are attracting or repelling

Question 18

Where are nuclear energy stores found?

Answer 18

Released through radioactive decay: fusion or fission

Question 19

What are the 4 methods of energy transfer?

Answer 19

> Mechanically
Electrically
By heating
By radiation

Question 20

How is energy transferred mechanically?

Answer 20

When a force MOVES an objects (work is done)

Question 21

How is energy transferred electrically?

Answer 21

When a charge moves through a potential difference

Question 22

How is energy transferred by heating?

Answer 22

When energy moves from a hotter object to a cooler object

Question 23

How is energy transferred by radiation?

Answer 23

e.g. microwaves, visible light. x-rays (often called light energy)

Question 24

Define Gravitational potential energy

Answer 24

Energy that an object has due to its POSITION

Question 25

How do you work out Gravitational potential energy, Ep?

Answer 25

Ep = mgh

Ep - J
m - kg
g - N/kg
h - m

Question 26

What is kinetic energy?

Answer 26

Energy gained as it is ACCELERATED by a force

Question 27

How do you work out kinetic energy of an object, Ek?

Answer 27

Ek = 1/2mv^2

Ek - J
m - Kg
v - m/s

Question 28

What happen to Ep as Ek increases?

Answer 28

Ep decreases

Question 29

What happens to Ek as Ep increases?

Answer 29

Ek decreases

Question 30

Define power

Answer 30

The rate of doing work

Question 31

What is a watt?

Answer 31

> Unit of power

> Joules per second

Question 32

How do you work out power in terms of energy?

Answer 32

P = W ÷ t

P - W
W - J
t - s

Question 33

What is 1kW equivalent to?

Answer 33

1000W

Question 34

How do you work out energy using power?

Answer 34

E = P x t

Question 35

How do you work out power using velocity?

Answer 35

P = Fv

P - W
F - N
v - m/s

Question 36

How do you work out the effiency of a mechanical system?

Answer 36

(Useful energy output ÷ Total energy input) x 100