Work and Potential Energy
When a force moves an object through a distance, energy is transferred and work is done.
- when something moves, something else puts effort in to move it
- the thing putting effort in needs energy, meaning it then does work by moving the object and energy recieved is transferred into other forms
:: object 1 moves --> object 2 supplies effort to move --> object 2 needs energy --> work is done when object 1 moves --> object 1 transfers energy recieved from object 2 into other forms
Both in Joules
W = F x d = Work done, joules = force, newtons x distance, metres
Gravitational Potential Energy
- due to height
Ep = m x g x h = Gravitational Potential Energy, joules = mass, kg x gravitational field strength, Newtons x height, metres
GPE is the energy that an object has by virtue of its vertical position in a gravitational field. When the object is raised vertically, work is done against the force of gravity and the object gains gravitational potential energy. On the Earth - gravitational field strength is 10 N/kg.
= energy of movement
Kinetic Energy = 1/2 x mass, kg x speed(2) ... Ek = 1/2 x m x v(2)
Kinetic energy of something depends on mass and speed. The more it weighs and the faster it goes, the bigger its kinetic energy will be.
Kinetic energy transferred = work done
when a car moves, it has kinetic energy, to slow a car down, this kinetic energy needs to be converted into other types of energy. to stop a car, the kinetic energy has to be converted to heat energy as friction between wheels and brake pads causing the temperature of the brakes to increase.
1/2mv(2) = F x d
m = mass of car and passengers, kg v = speed of car, m/s F = max braking force, N d = braking distance, m
Falling objects convert Ep into Ek - when something falls, its potential energy is converted into kinetic energy. The further it falls, the faster it goes.
Kinetic energy GAINED= potential energy LOST
some Ek is transferred into Heat and Sound