Simple Machines: Preparing for Play

Introduce the concept of simple machines using a classroom door! Students like to see how simple machines are a part of everyday life, and this is an easy way to illustrate that fact. Through the activity below, students will learn that a door is a type of lever. Depending on where you push on it, it takes more or less force (effort) to move it.

Start by placing a piece of masking tape near the hinge of the door halfway up the height of the door. Place a second piece of tape near the door knob at the same height as the first piece of tape. Place a third piece of tape in between the first and second pieces of tape making the three pieces of tape in a line.

Then, using one finger, have students take turns pushing on the piece of tape nearest to the hinge. Is it hard or easy? Repeat for the second and third pieces of tape.

What’s going on here? Well, because the door is a lever, it pivots on a fulcrum (the hinge). Work = Distance X Force, and because of that equation we know if we decrease the force, we have to increase the distance to get the same amount of work done. The distance is the length from the point we are pushing, from the fulcrum, and the force (effort) is pushing the door with your finger. Therefore, it should have been easiest to push the tape near the knob of the door, because it is the farthest from the hinge or fulcrum.

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