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Momentum - What is an Inelastic Collision?

Click here
to see the difference

between an elastic
collision and an inelastic
collision.

An example of an inelastic
collision is where

one car collides
with another and

both cars keep moving but stick
together after the collision.

For example, car 1
has

a mass of 1200
kg and travels with a velocity of
20 m/s.

Car 2 has
a mass of 800 kg and is
stationary.

Car 1 collides with car 2
and they both stick together.

What is the velocity of both
cars after the collision?

The total momentum before the collision is

momentum = mass x velocity

For car 1

momentum = 1200
x 20

=
24000 kgm/s.

For car 2

momentum = 800
x 0

=
0 kgm/s.

Total momentum
before the collision is

24000 + 0 = 24000 kgm/s.

The law of conservation
of momentum tells us that the

total momentum after the collision
is also 24000 kgm/s.

The mass of both
cars after the collision
is

1200 + 800 = 2000
kg.

The velocity of both
cars after the collision

can be calculated because

momentum
before = momentum after

24000
= 2000 x v

v = 24000
÷ 2000

= 12 m/s.

The total kinetic energy decreases with an inelastic collision.

You can use the equation
for kinetic energy

to see that the total kinetic energy

before the collision is 240,000J

and after the collision
it is 144,000J.

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