Quiz4U: Find the initial velocity?

Question

A car of mass 1,500 kg traveling at 34 m/s (parallel to the x-axis) collides head on with another car, with a mass of 2,500 kg, traveling in the oppisite direction. Suppose that upon impact both cars stop moving, so that their final velocities are both zero. Find the initial velocity (i.e. before impact) of the second car. Choose the closest answer.

Possible Answers:

-20.40 m/s

-22.93 m/s

-25.42 m/s

-27.12 m/s

-29.91 m/s

Answer 1

M1V1 +M2V2 = M(0)

(1500)(34) + (2500)(?) = 0

51000 = -2500?

?= - 51000/2500

?= -20.4...

Answer 2

..... by applying the law of conservation of momentum.

This question tests your knowledge of it, which is maybe nil?

Answer 3

V2 = -V1*m1/m2 = -20.4

Answer 4

The answer is -20.4

Both must have the same momentum ( mass x velocity)

so 1500 x 34 = 2500 x v

v = 1500 x 34 /2500 = 20.4