In a physics experiment, Stan has two lab carts. The blue lab cart has a mass of 0.5 kg and the red cart has a mass of 2.0 kg. In one experiment, Stan set the two carts at rest
on the track. He pushes in the plunger between them and releases it. He uses a
stopwatch to determine that after he releases the plunger, the red cart rolls to the right
at a velocity of 4 m/s.
Determine the velocity of the blue cart after the explosion.