A 5000-kg freight car crashes into a 10,000-kg freight car at rest. They couple upon collision and move with a speed of 2 m/s. What was the initial speed of the 5000-kg freight car?

6 m/s

Explanation:

mass of moving car m1=5000 kg

initial velocity of moving car vi1=?

mass of car at rest = m2=10000 kg

initial velocity of car at rest = vi2=0

final velcoities of both cars after collision = vf1=vf2 = 2m/s

using conservation of momentum rule

m1vi1+m2vi2=m1vf1+m2vf2

putting values

==> 5000 * vi1 + 1000 * 0 = 5000 * 2 + 10000 * 2

==> 5000 * vi1 = 2 * 15000

==> vi1 = 2 * 15000 : 5000

==> vi1 = 2*3=6 m/s