A 4.00 kg object is moving at 5.00 m/s EAST. It strikes a 5.00 kg that is moving WEST at 2.00 m/s. The objects collide elastically and move away in the EAST-WEST direction. The velocity of the 5.00 kg object after the collision is
A) 4.22 m/s EAST.
B) 2.78 m/s WEST.
C) 4.22 m/s WEST.
D) 2.78 m/s EAST.
E) 1.11 m/s WEST.

Question

Quizplus · Accepted Answer

Explanation:Momentum is conserved in the x-direction:$$4.00	ext{ kg}	imes5.00	ext{ m/s}+5.00	ext{ kg}	imes(-2.00	ext{ m/s})=4.00	ext{ kg}	imes v_{4	ext{ kg}}+5.00	ext{ kg}	imes v_{5	ext{ kg}}$$$$20.0	ext{ kg m/s}-10.0	ext{ kg m/s}=4.00	ext{ kg}	imes v_{4	ext{ kg}}+5.00	ext{ kg}	imes v_{5	ext{ kg}}$$$$10.0	ext{ kg m/s}=4.00	ext{ kg}	imes v_{4	ext{ kg}}+5.00	ext{ kg}	imes v_{5	ext{ kg}}$$$$v_{5	ext{ kg}}=\frac{10.0	ext{ kg m/s}}{5.00	ext{ kg}}=2.00	ext{ m/s EAST}$$

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