We’ve all heard about machines. We see them all around us every day helping us do our work. Did you know that there are simple machines that were discovered thousands of years ago? When we think of machines we think of big complex robots or cars, but these complex machines can be broken down into smaller simple machines.
A lever, inclined plane, wheel and axle, screw, wedge, and a pulley are examples of simple machines: things designed to reduce the amount of force we put into a task, but have another cost. (A force is a push or a pull.)
This month we will test inclined planes, also known as ramps. The question will be “How does the length of a ramp affect the force needed to move an object up it?”
A small chair or other short distance to place a ramp on, several different lengths of ramps (I used cut of lengths of cardboard, planks of wood… something to drag an object up), a ruler, a thin rubber band, two paper clips, and a small object to pull up the ramp (I had a Chinese food container with a metal hook, but you can use anything to hook the clips up to when you pull).
Assemble your force measuring device: Unfold two paper clips and attach them to the two ends. This will show how much force needed to move an object. If the rubber band stretches really far, that means a lot of force is used. If it only stretches a small bit, it is less force used.
Hang your small object to get the force needed to pull it straight up. Measure this distance and record it. To see this is the force needed to pull the object straight up, put the object on the floor beside the chair and lift it straight up. See how the rubber band pulls the same distance?
Place a short ramp from the ground up to the chair. Put the object and the rubber band device along the ramp. Be sure to pull the object up in the same direction as the ramp (not straight up). Measure the length of the rubber band this time.
Continue doing this with different ramp lengths to see how the rubber band changes length.
A simple machine makes it easier to do a task. You should have noticed the rubber band got shorter when you used a longer ramp. This means you used less force to pull it up to the same height. However, what did you have to do to get it up to that height? The longer ramp means you have to apply a smaller force over a LONGER distance. The shortest distance to move that object from the floor to the chair was not using a ramp. But that used the most force, over a short distance. It didn’t seem like much, but imagine putting a piano into a truck. You could lift the piano from the ground to the truck bed, or you could push the piano along a long ramp into the truck. The ramp has you putting less force in, over a bigger distance. Easier! Thanks, simple machines!
What can you change about this experiment? Heavier objects? Lighter? Different heights with the same ramp?
I hope you enjoyed this simple experiment. If you have more questions about this, specifically around the science fair aspect of this experiment, contact the author.
Steve Davala is a high school chemistry and physics teacher who likes to write and work with Photoshop. He’s got two kids of his own and subjects them to these science activities as guinea pigs. Follow him on Twitter or email him at firstname.lastname@example.org.