Pull back one ball and release, and you will see only one ball on the other side move from that reaction. If you pull back two balls, two balls will move. Try it and see for yourself! Every action has an equal and opposite reaction – see science demonstrated clearly and simply with a touch of amusement. Newton’s Cradle with wooden base and chrome frame and balls. Looks great on any desk in the home or the office. Also known as balance balls, these steel balls keep you entertained throughout the day. Pull back one or more of the balls and let them drop down.