A 4.00 kg object is moving at 5.00 m/s EAST.It strikes a 6.00 kg that is at rest.The objects have an elastic collision.The velocity of the 4.00 kg object after the collision is at an angle of 30.0 degrees SOUTH of EAST.The velocity of the 4.00 kg mass after the collision is
A) 5.78 m/s.
B) 4.56 m/s.
C) 3.55 m/s.
D) 1.67 m/s.
E) 2.66 m/s.

Question

Quizplus · Accepted Answer

Using conservation of momentum in the x-direction:
m1v1i = m1v1fcosθ + m2v2fcosφ
(4.00 kg)(5.00 m/s) = (4.00 kg)(v1f cos 30°) + (6.00 kg)(0)
v1f = 4.56 m/s

Therefore, the answer is B) 4.56 m/s.

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