Question

A 50.0 g toy car on a frictionless surface moving at constant velocity (moving 1.0 m in 0.25 seconds) collides with and bounces off of a stationary 100.0 g toy car. The 50.0 g glider bounces back (moving 1.0 m in 2.0 seconds) and the 100.0 g glider continues moving forward (going 1.0 m in 0.75 seconds).

a) Is momentum is conserved in this collision? Show all of the work required to determine this.

b) Is the collision completely elastic? Explain in terms of the calculated values for kinetic energy before and after the collision.

Answer 1

The mass of glider m1 = 50g = 0.05kg , mass of car m2 = 100 g = 0.1 kg

The initial velocity of the glider is u1 = + 4 m/s

The initial velocity of the car is u2 = 0 m/s

The final velocity of the glider is v1 = - 0.5m/s

The final velocity of the car is v2= +1.33 m/s

a) the total initial momentum = m1u1 + m2u2 = 0.05(4) + 0.1(.0) = 0.2 kg m/s

   the total final momentum = m1v1 + m2v2 = 0.05(-0.5) + 0.1(1.33) = 0.108 kg m/s

as the final momentum is not equal to the initial mometum so momentum is not conserved

b) the total initial kinetci energy = 0.4 + 0 = 0.4 J

the total final kinetic energy = 0.00625 + 0.088 = 0.095 J

as the final KE is not equal to the initial KE so KE is not conserved