500 g ball of putty moving horizontally at 5 m/s collides with and sticks to a block lying on a frictionless horizontal surface. If 45 % of the kinetic energy is lost, what is the mass of the block

A railroad car of mass 2.85 x 10^4 kg moving at 2.60 m/s collides and couple with two coupled railroad cars, each of the same mass as the single car and moving in the same direction at 1.20 m/s.  A. How much kinetic energy is lost in the collision.

A box of mass 4.8 kg slides on a horizontal frictionless table and collides with another box of mass 3.0 kg, which is initially at rest at the edge of the table. The speed of the 4.8 kg box before collision is 4.0 ms−1, and the height of the table is 0.80 m. If the two boxes stick together after colliding, what is their kinetic energy at the instant just before they strike the floor?

A railroad car of mass 2.5 x 104 kg is moving at a speed of 4.00 m/s.  It collides and couples with three other coupled railroad cars, each with the same mass as the single car, moving in the opposite direction at 2.00 m/s.  (a) What is the speed of the four coupled cars after the collision? (b) How much energy is lost in the collision?