Science Projects Using Two Pulleys

Pulleys are often used in science experiments.

Pulleys are a tool used in science to help students understand weights and measurement. Students can make their own pulley system to understand how the pulley pulls weight, or they can use ready-made pulleys with a spring scale to understand pressure and weight resistance. Pulleys are fun and easy for a full classroom of students to use.

Simple Homemade Pulleys

Use coat hangers and spools to make homemade pulleys. Gather four spools, two round pencils, two metal coat hangers, wire cutters, ribbon, a small pail and a spring scale. Begin by cutting the flat bottoms off the coat hangers. Place two spools on each pencil then place the pencil on the bottom of the coat hanger. Wrap the metal around the pencil to attach the pencil to the coat hanger. Secure the ribbon to one end of one of the pencils, then begin to wrap the ribbon around the spools. For ease, the hangers will be labeled one and two. If the ribbon is tied to the pencil on hanger one, wrap the ribbon around the spool on hanger two closest to the ribbon's knot. Wrap the ribbon around to the spool closest to the ribbon knot on hanger one. Keep going to the spool farthest from the knot on hanger two. Wrap around to the spool farthest from the knot on hanger one. Wrap around the top and drag the ribbon to the side of the contraption and attach the spring scale. The hanger hooks will be facing away from each other, so one end can be attached to a ceiling and the other end can be attached to the bucket. Use the new contraption to test the strength of different ribbons and ropes used with pulleys.

Return Pulley System

Conduct an "elevator" on a tree with two pulleys, rope, a bucket, three S-hooks and 6 inches of PVC pipe. Loop the rope around a tree branch, then connect the two pulleys to either end of the loop with S-hooks, near the branch. There should be plenty of rope slack on either side of the branch. Connect one of the pulleys to the bucket with an S-hook. Tie a length of rope to the basket handle, then lace the rope through one tree pulley, down through the pulley attached to the basket, then back through the second tree pulley. Thread the PVC pipe onto the end of the rope and tie it off to form a handle. Use the pulley to move objects from the ground to the tree.

Lift the Bucket

Gather two double pulleys, rope, a bucket and a spring scale. Double pulleys are two pulleys next to each other in a block. Arrange the pulleys by attaching one pulley to a stable surface which can bear the weight of a full bucket, such as a ceiling beam. Attach rope to the top pulley and begin to string the pulleys together. The rope passes from the top pulley then around the first pulley in the bottom block. The rope then passes over the first pulley in the top block and to the second pulley in the bottom block. The last piece of rope passes over the second pulley on the top block. A length of rope should protrude from the top to hang down the side of the pulleys, while a length hangs from the bottom pulley. Tie the bucket, filled with water, to the bottom pulley. Tie the spring scale to the top pulley. Pull the spring scale until the bucket leaves the ground. Measure the inertia needed to lift the bucket off the ground.

Cardboard Pulleys

Pulleys can be made from cardboard. Gather corrugated cardboard, a compass, scissors, nails, wood glue, small nuts and bolts, a wire cutter, pliers and a coat hanger. Use the compass to draw and cut out two 4-centimeter circles on the cardboard. Draw and cut a third circle measuring 2 to 3 centimeters. Punch a hole through the center of each circle with the nail, and place all three circles on the nail with the smallest circle in the middle. Glue all circles together and allow to dry, then remove the nail. Cut the clothes hanger to create a wire measuring 20 centimeters and bend it to form an arc. Place one end of the arc on the bolt, then press the bolt through the hole in the cardboard. Place the other end of the arc on the other end of the bolt, then attach the nut. Work the pulley to make sure it spins freely. Loosen the nut if necessary.

References

• Easy Science Experiments: Machines: Return Pulley System
• Science Buddies: Give Yourself A Lift: Lightening the Load with Pulleys
• The Science Notebook: Simple Machines: Part Two