| An inelastic
collision is one where the final KE of the system is different from the initial KE.
A basketball dribbled against a concrete floor distorts, momentarily comes to rest, and
then springs back, popping into the air. This squashing produces some internal
heating as the molecules shift position, and even the sound of dribbling the ball carries
a bit of energy. Thus, resulting in bouncing less than the original height.
If, after an impact between two macroscopic objects, either one increases in temperature
or remains distorted, the collision is inelastic. The completely inelastic collision is at one extreme, where the impacting
objects stick together, and the maximum amount of KE is transformed. For example, a
egg fallen on to the floor. Less drastic case is where the colliding objects bounce
apart and yet lose KE in the process.When two objects of mass m1 and m2,
initially moving with speeds v1i and v2i, collide head on and fly
off with speeds v1f and v2f, initial momentum equals final momentum,
and
m1v1i + m2v2i
= m1v1f + m2v2f
The head on restriction requires that the
motion of both bodies at the moment of impact be along a common straight line connecting
the two centers of mass. As a result, the final motion is also along that line.
But if the collision takes place off center, then the motion will have x and y
direction. Their momentum will still be conserved, however, in an angled direction.
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The loss of energy generally runs
a system down. In this case, a bouncing golf ball. With each impact, a certain
amount of energy goes into random thermal motion, warming the ball and floor; less is
returned as organized KE to the ball, so it rises more slowly and doesn't bounce as high.
The closer the images of the ball, the slower it's moving. |
