Question

A 2250 kg car traveling in the neagtive x direction at 8.5 m/s strikes a second car of mass 2830 kg which is moving. The first rebounds and moves off with a speed of 2.7 m/s. After the collision, the second car moves in the negative x direction at 3.2 m/s. What was the original speed and direction of the second car? Explain your reasoning.

Then how much kinetic energy was lost in the collision?

Answer 1

Here ,

let the initial velocity of second car was u2

Using conservation of momentum

2250 * (- 8.5) + 2830 * u2 = 2250 * 2.7 - 3.2 * 2830

solving for u2

u2 = 5.71 m/s

the original velocity of second car is 5.71 m/s in the positive x direction

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lost in kinetic energy = initial kinetic energy - final kinetic energy

lost in kinetic energy = 0.50 * 2250 * 8.5^2 + 0.50 * 2830 * 5.71^2 - (0.50 * 2250 * 2.7^2 + 0.50 * 2830 * 3.2^2)

lost in kinetic energy = 104725 J

the lost in kinetic energy is 104725 J