A 40ton rail car and a 80ton rail car, initially at rest, are connected together with a giant but massless compressed spring between them. When released, the 40ton car is pushed away at a speed of 4.8m/s relative to the 80ton car.

What is the speed of the 40ton car relative to the ground?

Which feature indicates that mars resides in the inner region of the solar system

If 21.2 kcals of energy is released by this reaction, how many kj does the reaction release? (1 cal 4.184 j)

Asap and show ! a 14 kg rock starting from rest free falls through a distance of 5.0 m with no air resistance. find the momentum change of the rock caused by its fall and the resulting change in the magnitude of earths velocity. earth mass is 6.0 * 10^24 kg. show your work assuming the rock earth system is closed.