In Part 1, we talked about the different types of simple machines and how to identify them in the objects around us and even part of our bodies. You can also make use of everyday items in the home for some ‘simple machine exploration’! Here are two simple experiments to try.

Rice Push Challenge

In this experiment, we learn more about wedges. A wedge is a simple machine that is actually part of a subset of inclined planes. inclined planes make it easier to raise things, but when an inclined plane is used as a wedge, what happens? Let’s find out.

You need:

• A Large and deep tray filled with uncooked rice
• A Rectangular block (a LEGO@ or wooden construction block)
• A Triangular block (a LEGO@ or wooden construction block)

What to do:

1. Place the tray of rice on the table and run your hand over the surface so that the rice is  smooth and evenly distributed.
2. Place the rectangular block in the rice at one end of the box. Most of the block should be totally covered by the rice.
3. Get your child to push the block to the other end of the tray, paying close attention to the amount of effort used. See what happens to the rice.
4. Repeat the experiment using the triangular block this time. Ensure that the ‘sharp’ point of the triangle is facing the other end of the tray, and push it towards the opposite end.
5. Ask your child: Is it easier to push the triangular block or the rectangular block? What happened to the rice in both situations?

Wedges like the triangular block are inclined planes that split things apart. Notice how the rice grains are ‘pushed apart’ when we move the triangular wedge through the rice. Knives are also wedges. Bows of boats and ships are shaped like wedges, which make it easier for them to move forward in the water. When wedges are used to push things apart, they help to reduce the force needed to do this.

Bamboo Pole Pulleys

We use pulleys everywhere – at home, at work, in buildings and construction sites. Your schoolgoing child sees a pulley at work every morning during the flag raising ceremony! Pulleys help to reduce the amount of force needed to do work or to change the direction of the force.  You don’t need special equipment to demonstrate the usefulness of pulleys – try out the following experiment with items from your kitchen.

You need:

• A bamboo pole
• 2 chairs
• 2 extra-large clothespegs
• a smooth rope
• A plastic milk jug with a handle (or a detergent bottle with a handle), filled with water or beans

What to do:

1. Secure the ends of the bamboo pole to the tops of two chairs using the clothespegs. Have a gap of about 1 metre between the two chairs.
2. Hang the rope over the pole and tie one end to the handle of the jug.
3. Ask your child to pull down on the other end of the rope. Notice that the jug gets lifted up?
4. Untie the milk jug. Push one end of the rope through the handle of the jug, and then tie that end of the rope to the pole.  Ask your child to lift up the loose end of rope to lift up the milk jug. Now, is it easier to lift up the jug, compared to the amount of force that was used in Step 3?
5. Loop the loose end of rope over the pole and pull the end down to lift the milk jug.  What you have done now is to create a combination of movable and fixed pulley systems. Does this arrangement make it easier to lift the milk jug?

In Step 3, you created a fixed pulley system that is used to change the direction of the force needed to lift the milk jug. In Step 4, you created a movable pulley system. You will notice that different combinations of pulley systems will change the amount of force needed to lift the jug. You can also try to loop the loose end of the rope over the pole a few times and see if it gets easier to lift up the jug.

Would you like to suggest other simple machine experiments? Do share your ideas with us.

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