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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 velocity^{2}

this is usually written
as KE = ½mv^{2}

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 12^{2}

= 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
2^{2} = 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

Links Energy Transfer Revision Questions

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