Work, Efficiency & Power

Question 0

Energy

Answer 0

Energy is the ability to do work

Question 1

Work

Answer 1

Work is done when energy is transferred from one form into another

Question 2

Power

Answer 2

The rate (1/t = per second) of doing work

Question 3

Mechanical work equation

Answer 3

W = f x d
Joules = Newtons x Distance
J = N x m

Question 4

Renewable energy

Answer 4

Will not run out

Question 5

Non - renewable energy

Answer 5

Once the energy source is used up, it cannot be replaced

Question 6

Secondary energy form

Answer 6

Transforming energy from one form into another ie wind power

Question 7

Give examples of renewable energy sources

Answer 7

Hydroelectric
Wind power
Tidal power
Geothermal energy

Question 8

Give examples of non renewable energy

Answer 8

Coal
Oil
Natural gas
Nuclear energy

Question 9

Energy transfer diagram for a hydroelectric plant

Answer 9

Water with gravitational potential + when dropped down powers turbines (kinetic) –> electrical energy + thermal energy + sound energy

Question 10

Which axis does the independent variable go on

Answer 10

X axis

The cause

Question 11

Which axis does the dependent variable go on

Answer 11

Y axis

The effect

Question 12

What is the equation to calculate the energy objects have when they move

Answer 12

Ek = 1/2 mv(sq)
Kinetic energy = 1/2 x mass x velocity (sq)
J = 1/2 x kg x m/s(sq)

Question 13

Gravitational potential energy equation

Answer 13

GPE = mgh
GPE = mass x gravity x height
J = kg x N/kg x m

Question 14

Gravity

Answer 14

G = 10N/kg

On earth

Question 15

What happens when you drop a ball

Answer 15

• the ball starts with GPE
• GPE decreases as gets closer ground
• GPE converted into kinetic energy
• ball accelerates as gains kinetic energy (the increase in kinetic energy is qual to the decrease of GPE)
• all GPE converted to kinetic energy when about to hit ground
• during bounce, kinetic energy converted into elastic potential energy
• some energy is transferred into the surroundings in form of sound/heat
• ball converts elastic potential back into kinetic energy
• kinetic converted into GPE as ball rises (ball slows down as height increases)
• at the peak of the bounce, all kinetic into GPE
• the peak of bounce isn’t as high as where it was dropped from as some been transferred into surroundings (sound and thermal)
• the ball will eventually come to a rest on the ground (all GPE given has now been transferred into surroundings)

Question 16

Conservation of energy

Answer 16

Energy cannot be created or destroyed but only transferred into other forms of energy

Question 17

Power equation

Answer 17

Power = work done/time taken

Watt (J/s) = J/s

Question 18

Efficiency equation

Answer 18

E (%) = [(useful power (or energy) output/total power (or energy) input) x 100]