A railroad car moving at a speed of 3.10 m/s overtakes, collides and couples wit

Question

A railroad car moving at a speed of 3.10 m/s overtakes, collides and couples with two coupled railroad cars moving in the same direction at 1.40 m/s. All cars have a mass of mass 3.3 times 10^4 kg. Determine the following. speed of the three coupled cars after the collision (Give your answer to at least 2 decimal places.) m/s kinetic energy lost in the collision Knowing the mass of each car and its speed before and after the collision, can you determine the initial and final kinetic energy and then the kinetic energy lost in the collision? J A 103-g wooden block is initially at rest on a rough horizontal surface when a 12.8-g bullet is fired horizontally into (but does not go through) it. After the impact, the block-bullet combination slides 6.5 m before coming to rest. If the coefficient of kinetic friction between block and surface is 0.750, determine the speed of the bullet immediately before impact.

Explanation / Answer

m1 =m2 =m3 3.3*10^4 kg , u1 =3.1 m/s, u2 = 1.4m/s, v = 1.967 m/s

Energy lost = change in kinetic energy

K1 - K2 = (1/2)m1u1^2 +(1/2)(m2+m3)u2^2 - (1/2)(m1+m2+m3)v^2

K1 -K2 = (0.5*m)(u1^2 +2u2^2 -3v^2)

K1 - K2 = (0.5*3.3*10^4) ((3.1*3.1)+(2*1.4*1.4) - (3*1.967*1.967))

K1- K2 = 31725.1 J

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