A3 kg toy car with a speed of 7 m/s collides head-on with a 2 kg car traveling in the opposite direction with a speed of 5 m/s. if the cars are locked together after the collision with a speed of 2.20 m/s, how much kinetic energy is lost?

Answers:

kinetic energy lost = 86.4J

Explanation:

let Kf be the kinetic energy after the collision and Ki be the kinetic energy before the collision. let the 3kg car be 1 and 2kg car be 2.

Kf = K1(f) + K2(f)

Ki = K1(i) + k2(i)

loss in kinetic energy = Kf - Ki

                                 = 1/2(3)(2.20)^2 + 1/2(2)(2.20)^2 - 1/2(3)(7)^2 - 1/2(2)(-5)^2

                                 = 12.1 - 98.5

                                 = -86.4 J

therefore, the kinetic energy lost in the collision is 86.4 J.