To demonstrate the independence of velocity components in a dramatic way.
Funnel cart with ball on track, as photographed.
Follow this demonstration with C2-26: FUNNEL CART WITH MASS OVER PULLEY, AND C2-27:FUNNEL CART ON INCLINE.
A ball is placed in the funnel and the funnel cocked by compressing a spring. The cart is then pushed across the track. At a certain point a bump below the track trips a lever, releasing the spring and ejecting the ball vertically. Because the ball and the cart both move with the same horizontal speed, the ball stays directly above the funnel at all times, and falls back into the funnel. Before doing the experiment, ask your students where the ball will fall: in front, behind, or in the funnel.