Explore how cranes work by building a simple crane arm, then testing different loads to see how much work it takes to lift them!
What You Need
- 2-ft. piece of string
- Small items to lift using the crane (such as keys or washers)
What You Do
- Tie one end of the string around the center of the pencil.
- Stick the other end of the string through the hole at one end of the ruler, then tie a paperclip to the end of the string. Bend the paperclip out a little to make a hook.
- Hold the ruler at an upright 45-degree angle away from you. The pencil should lay perpendicular across the base of the ruler, with the paperclip hanging straight down.
- Roll the pencil between your fingers to raise and lower the paper clip. This is similar to how real cranes work. The arm (ruler) needs to be stiff, so it can hold the heavy load while the take-up reel (pencil) winds the cable to lift the load.
- Try out your crane and see how much work it takes to lift one, two or more small objects.
What Else to Do
Try attaching your crane arm to a cardboard box. Here are some supplies you might use to do it: tape, strips of corrugated cardboard and an empty thread spool. If your crane does not work exactly as you planned, redesign and test it until it does.
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