The classic physics problem of two train cars running into each other... Take a look at the conservation of linear momentum and loss of kinetic energy in an inelastic collision. Calculate the final velocity of two colliding objects. We will do this by applying Newton's laws to see that linear momentum is conserved in an inelastic collision but mechanical energy is lost in this type of collision. This problem typically comes up in high school and introductory college physics courses as as a part of linear momentum. This problem can be found in AP Physics as well as on the JEE exam.