Work and Potential Energy

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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  

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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. 

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Kinetic Energy

= 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 

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Kinetic Energy

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 

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