## The Pulley

Now that Pic and Harry have the blocks of stone at the construction site they have encountered a new challenge. They must lift the stones into position on top of the previous stones.

They are unable to build a lever with a tall enough fulcrum to lift the stones into place safely and Pic is sure there has to be a better way than building more inclined planes.

Pic wants to secure a rope around each end of the stone and he and Harry will lift the stone into place. Harry has his doubts about this but agrees to try anyway.

Pic decides to experiment,

He secured one end of the rope to the beam.

He loops the rope through a rope tied around the stone.

He put the end of the rope over the beam and pulled to see if he could move the stone. Watch Pic to see what happens.

Talk Now - 2e

Why do you think this worked? Discuss this with your partner then record your best explanation in your lab packet using complete sentences.

Remember Pic was barely able to lift his end of the stone when Harry was helping him. Has Pic suddenly gotten stronger?

What Pic has created is a crude pulley system. A pulley is a simple machine that can be used to change the direction of an applied force and when used in certain combinations can let us apply less force to accomplish work.

Let's investigate the use of a pulley system.