Science Experiments for Kids : Inclined Plane Experiment

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We did a simple yet popular science experiment for kids to demonstrate the mechanical advantage of using an inclined plane. { All science experiments for kids here}

Materials

Wooden Plank
Rice/Beans
Plastic bag
Rubber band
Tape Measure
Stack of Books

Our load is going to this sack of rice. Place a good quantity of rice in a plastic bag and tie a heavy duty rubber band around it. Then take another rubber band and cut it. Now tie this cut rubber band around the plastic bag and suspend the bag.

Load = rice bag

Work = to lift it up to the top of the book stack

Scenario 1:

Pull the bag of rice using the rubber band to the top of the stack of books. The rubber band stretches showing the amount of effort needed to get the work done.

Measure the stretch of the rubber band as soon as the bag hits the top of the stack of books.

Scenario 2 :

Now place the load at the bottom of the wooden plank propped against the stack of books {this is your inclined plane}. Pull the same load using the rubber band over the inclined plane. Visually you can see that the rubber band is not stretching as much as it did when you tried to pull it up without the use of an inclined plane.

To make things clearer, measure the stretch of the rubber band once the load reaches the top. It will be lesser than the measurement you got in scenario 1.

Scenario 3:

Here we are making the effort needed for the work even lesser. We use a smoother inclined plane, a foam board. Prop the foam board against the same stack of books. Pull the load up against the board to the top of the stack. Measure the stretch of the rubber band and you will see that the measurement is even lesser than the measurement in scenario 2.

Why? In Scenario 2, the wood offers some resistance to the load being pulled. There is some amount of surface friction. In the third scenario the surface friction is drastically reduced by using a much smoother material as an inclined plane. In effect you are using lesser force over the same distance as scenario 2.

Other than the material itself, more importantly if you compare the pictures, the the angle of inclination is much lower when I used the foam board. Simply put, the foam board is not as steep as the wooden plank. BUT the distance traveled by the rice bag will be higher. HOWEVER, the effort needed to pull the load will be smaller. That’s your trade off.

Smaller amount of effort needed over longer distance makes life simple- the basic idea of simple machines.

To put things in perspective we did the same experiment on a larger scale for better understanding.

We tried to lift a big box of books to the height of the slide. The effort needed to accomplish the work was very high.

Then the same box was lifted to the same height using the inclined plane

What is happening there?

The rubber band experiment is just a simplified demonstration.

In real world, simple machines like the one demonstrated above makes us humans exert as little effort as possible. At what cost? distance ! At the end, work done { Force * Distance} will be the same. But life will be much easier with simple machines since the force exerted is much lesser.

If you want to calculate the actual mechanical advantage of using an inclined plane you do so by dividing the measurement you get in scenario 2 or scenario 3 by the measurement you get in scenario 1. In our case it was { 24/20} { Slope / Height}