revision unit 5 Flashcards
what is work done
work done happens very times an object is moved. it is the energy transferred from a force
work = force x distanced moved by the object
what is power
the work done per minute, and its measured in watts, kilowatts, or megawatts
power = word done/time taken
what is gravitational potential energy?
it is the energy stored in an object because of position in the earth gravitational field, an object gravitational potential energy would increase if an objects up, and it decreases if an object moved down
equation = Ep= m x g x h
what is conversation of energy
it is a even energy is transferred to another form of energy since energy isn’t created nor destroyed
explain how energy is transferred in bungee jumping
the person would start with gravitational potential energy, and when they jump off it would turn into kinetic energy when the rope stretches once it hits the bottom the energy would change to elastic energy
what is kinetic energy
it is the energy that an object has because of its motion, kinetic energy depends on mass and speed of an object
kinetic energy = 1/2 x mass x speed^2
what is elastic potential energy
it is energy stored in an elastic object when work is done on it to change its shape
Ee = 1/2 x spring constant x extension^2
what is useful energy
it energy transferred to where it wanted
what is wasted energy
energy not transferred usefully
what is the relation between energy and spreading out
energy becomes less useful the more it spreads out.
wasted energy is transferred to the surroundings, and useful energy is eventual transferred to the surrounding
what is a Sankey diagram
it is a diagram that represents the energy flow in a system. it shows useful energy and wasted energy
what is the efficiency of the equation
efficiency = (useful power out/ total power in) x 100%
no machine can be more than a 100% because you cant get more energy than you put in
how is energy wasted in brake discs
when the pads get pushed down on the discs to stop the car some of the energy is transferred as wasteful heat
why is energy is wasted in machines and how can we reduce it
- friction between moving parts cause heat, you can reduce that by rubricating the parts
- air resistances causes energy transfer by heating to the surroundings, you can reduce that by streamline the shape of the car
- sound created by machinery transfers energy to the surrounding, you can reduce that by tightening loose parts reducing vibration
