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Energy Transfer

What is Kinetic Energy?

Anything that moves has kinetic energy, written as KE
(see also the pages on momentum).
The amount of kinetic energy that an object has
depends on how fast it is moving (its velocity)
and it also depends on the mass of the object.

Kinetic Energy = 0·5 x mass x velocity²

this is usually written as    KE  =  ½mv²

This equation is important!

For example, an object of mass 500kg has
a velocity of 12 m/s, what is its kinetic energy?

KE = 0·5 x 500 x 12² 
= 36,000J.     
(See also the KE of a Car).

The kinetic energy of an object is directly proportional
to its mass. This means that if you double the mass
you also double the kinetic energy (for the same velocity).

The kinetic energy of an object is proportional to
its velocity squared.
This means that if you double the velocity, you
multiply the kinetic energy by 2² = 4 (for the same mass).
This has implications for the braking distance of a car.

When a car is stopped by the force of applying the brakes,
the kinetic energy of the moving car must be transferred
into another form. After the car has stopped moving,
all of its kinetic energy has been transferred into heat.
The relationship between energy, force and distance is

Energy = Force x Distance

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