- To illustrate Newton's Third Law of Motion, using revised devices.
Insert the bolt/spring in the launch tube, with threaded end toward the brass washer.
Install the steel plate over the protruding end of the bolt, while facing the smaller slot downwards.
Grasp the threaded bolt with the fingers and pull against the spring pressure until the groove in the bolt is visible.
Pull the steel plate upward to engage the smaller slot with the groove. (CAREFUL! The bolt is now "armed".)
Set the cart on the floor or a long table.
Using the wood piece, carefully tap the top edge of the steel plate until the bolt is released.
Observe that the cart is accelerated backwards at the same time the bolt is ejected forwards, confirming Newton's Third Law.