Find out how to make three different kinds of lever in these experiments. The first is a can crusher that uses a lever action to squash a can. The second is a gripper for picking up small objects, just like a pair of tweezers. It can also work as a nutcracker. In a pair of nutcrackers, the load (in this case a candy or a nut) is between the pivot (the pencil) and the effort (where you push). In a pair of tweezers, the effort is between the pivot and the load.
The third experiment is a balance scale. It is like the ones used by the Romans about 2000 years ago. It works by balancing the weight of an object against a known weight, in this case a bag of coins. The coins are moved along the lever arm, until they balance the object being weighed. The farther away from the pivot the weighed bag is, the greater turning effect it has on the lever arm. The heavier the weight being measured, the farther away the bag must be moved to balance the arm. The weight is read against the scale along the arm.
Two short planks of wood about 16 x 4in and ½ - ¾in thick, hinge, screwdriver, two coffee-jar lids, glue, empty can.
To crush a can, put the can in between the lids, so that it is held in place. Press down hard on the top piece of wood.
Short pencil, two pieces of wood each about 6in long, thick rubber bands, objects to pick up or squash, such as candies or nuts.
Thick card about 20 x 3in, thin card, scissors, string, ruler, hole punch, 4 ½in circle of card, tape, 4oz of coins, felt-tipped pen, objects to weigh.
To weigh an object, put it in the cone and slide the envelope of coins backward and forward along the arm, until the arm balances. Each mark along the scale equals 2oz. In this picture, the object being weighed is about 3oz.
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