You give a shopping cart a shove down the aisle. The cart is full of groceries and has a mass of 30 kg. The cart accelerates at a rate of 2 m/s^2. How much force did you exert on the cart?

Arailroad car collides with and sticks to an identical railroad car that is initially at rest. after the collision, the total kinetic energy of the two cars is a) the same as before. b) half as much as before. c) one third as much as before. d) one fourth as much as before. e) twice as much as before.