Olaf is standing on a sheet of ice that covers the football stadium parking lot

Question

Olaf is standing on a sheet of ice that covers the football stadium parking lot in Buffalo, New York; there is negligible friction between his feet and the ice. A friend throws Olaf a ball of mass 0.400  kg that is traveling horizontally at 12.0  m/s . Olaf's mass is 70.8  kg .

Part B

What fraction of the initial kinetic energy was lost in this perfectly inelastic collision? Giver answer as a percentage.

Part C

If the ball hits Olaf and bounces off his chest horizontally at 7.40  m/s in the opposite direction (ouch!), what is his speed vf after the collision? Giver answer in cm/s.

Part D

What fraction of the initial kinetic energy was lost in this inelastic collision? Giver answer as a percentage.

Explanation / Answer

(B) for perfectly inelastic collision, Both will move together.

Applying momentum conservation,

0.40 x 12 = (70.8 + 0.4) v

v = 0.067 m/s

Ki = 0.4 x 12^2 /2 = 28.8 J

Kf = (70.8 + 0.4) (0.067^2) /2 = 0.16 J

Klost = Ki - Kf = 28.64 J

fraction = klost / Ki = 0.994

(C) Applying momentum conservation,

0.4 x 12 = 0.4 x (-7.40) + 70.8v

v = 0.11 m/s

(D) Ki = 28.8 J

Kf = (0.4 x 7.40^2 /2) + (70.8 x 0.11^2 /2 )

= 11.38

Klost = 17.4 J

fraction = 17.4 / 28.8 = 0.61

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