3. Im The 25,000 kg boxcar on the left is moving at 4.00 m/s to the right. The 3

Question

3. Im The 25,000 kg boxcar on the left is moving at 4.00 m/s to the right. The 30,000 kg boxcar on the right is moving at 7.00 m/s to the left. They collide and stick together. A) B) C) Find the kinetic energy of the boxcar on the right before and after the collision. D) What new mass(es), if any, for the boxcar on the right would result in it having a speed of What is the velocity of the boxcars after the collision? Find the kinetic energy of the boxcar on the left before and after the collision. 1.50 m/s after the the collision?

Explanation / Answer

Part A.

In this type of collision:
using moment conservation
Pi = Pf
m1v1 + m2v2 = M*V
where M = m1 + m2
V = (m1v1 + m2v2)/(m1 + m2)

v1 = +4 m/sec

v2 = -7 m/sec

V = (25000*4 - 30000*7)/(55000) = -2 m/sec

Velocity after collision = 2 m/sec towards left.

Part B

Initial KE of boxcar on left

KE1i = 0.5*m1*v1^2 = 0.5*25000*4^2 = 200000 J

Final KE of boxcar on left

KE1f = 0.5*m1*V^2 = 0.5*25000*(-2)^2 = 50000 J

Part C

Initial KE of boxcar on right

KE2i = 0.5*m2*v2^2 = 0.5*30000*(-7)^2 = 735000 J

Final KE of boxcar on right

KE2f = 0.5*m2*V^2 = 0.5*30000*(-2)^2 = 60000 J

Part D

Incomplete information.

It would depend on whether the direction of speed of boxcar on the right is in left or right.

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