Work, Efficiency & Power Flashcards
Energy
Energy is the ability to do work
Work
Work is done when energy is transferred from one form into another
Power
The rate (1/t = per second) of doing work
Mechanical work equation
W = f x d Joules = Newtons x Distance J = N x m
Renewable energy
Will not run out
Non - renewable energy
Once the energy source is used up, it cannot be replaced
Secondary energy form
Transforming energy from one form into another ie wind power
Give examples of renewable energy sources
Hydroelectric
Wind power
Tidal power
Geothermal energy
Give examples of non renewable energy
Coal
Oil
Natural gas
Nuclear energy
Energy transfer diagram for a hydroelectric plant
Water with gravitational potential + when dropped down powers turbines (kinetic) –> electrical energy + thermal energy + sound energy
Which axis does the independent variable go on
X axis
The cause
Which axis does the dependent variable go on
Y axis
The effect
What is the equation to calculate the energy objects have when they move
Ek = 1/2 mv(sq)
Kinetic energy = 1/2 x mass x velocity (sq)
J = 1/2 x kg x m/s(sq)
Gravitational potential energy equation
GPE = mgh GPE = mass x gravity x height J = kg x N/kg x m
Gravity
G = 10N/kg
On earth
What happens when you drop a ball
- 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)
Conservation of energy
Energy cannot be created or destroyed but only transferred into other forms of energy
Power equation
Power = work done/time taken
Watt (J/s) = J/s
Efficiency equation
E (%) = [(useful power (or energy) output/total power (or energy) input) x 100]