Activity 1: Newton's Second Law 1. Place two books close together on the table near the clamp pulley, one on either side of the string. Place them close enough to the clamp to prevent the cart from running into the pulley. Make sure the books do not interfere with the movement of the string. 2. Remove the rubber stopper and circular spring from the cart if attached. Use caution when removing the spring, as it can decompress quickly and become a projectile. 3. Tie a string to the cart through the hole where the rubber stopper was attached. 4. Place the cart on the table so the front edge rests against the stopping books. 5. Thread the string over the pulley and down to the floor. 6. Unbend a paperclip to make a hook where you can suspend the washers. See Figure 3. 7. Cut the string near the floor and tie the free end of the string to the paperclip. When the front edge of the cart rests against the books and the string is threaded over the pulley, the paperclip and the washers will be suspended just above the floor