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Gravitational Potential Energy to Kinetic Energy.

When an object with Gravitational Potential Energy starts to
fall,

its GPE is transferred into
Kinetic Energy.
The further

the object falls, the
less GPE it has and the
more KE it has.

When the object hits the ground,

all of its GPE has been
transferred into KE.

Some processes transfer GPE to KE to GPE to KE and so on.

Examples are a bouncing ball, a
pendulum and a
comet.

If we know the Height of a Falling
Object,

what will its Velocity be when it Hits
the Ground?

If we look at the example of the
75 kg rock

4·0 metres above the ground,

we can calculate that it has 3000J of GPE.

Using the equation for KE, we can

calculate how fast it is
travelling when it hits the ground.

All of the rock's GPE has become KE,

so the rock has 3000J of KE when it
hits the ground.

KE =
½mv^{2}

3000
= 0·5 x 75 x v^{2}

v^{2} = 3000 ÷ (0·5 x 75)

= 80

v
= 80

= 8·94 m/s.

How much Time will a Falling
Object take to Hit the
Ground?

Since we
now know how fast the rock was travelling,

we can calculate how
long it took to fall the 4·0 metres.

Try it using the equation for acceleration.

a = 10
m/s^{2} (for gravity), v
= 8·94 m/s, u = 0

(the answer is t = 0·894
seconds).

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