Kids love to play tricks on their friends and physics provides the perfect opportunity. While some of the experiments might look like magic, all of them follow the physical laws that we live by every day. The study of physics encompasses everything we do that has to do with matter, space, time, and energy.
CANTILEVER BRIDGE
Stack six notebooks on the edge of a table. Slide the top book halfway out over the tables edge. Once it balances push it back a little. Repeat this with the second book, sliding it halfway out until it balances, then pushing it back a little. Continue the same way until all six notebooks are staggered over the edge of the table. The top notebook appears to be suspended in air, yet it doesn’t fall.
Why? You have found the center of gravity, the point at which all the weight of an object seems to be concentrated. Thought the stack of books appear to be suspended, more than half the weight of the books is resting on the table.
INFLATING A BALLOON WITHOUT BLOWING INTO IT
Place the end of a deflated balloon over the top of an empty soft drink bottle. Make sure the balloon is secure and covers the entire top of the soft drink bottle. The balloon should hang to the side, deflated.
Place the balloon in cold water for five minutes, then place the bottle in warm or hot water. Watch what happens to the balloon. Put the bottle back into the cold water again. You can move the balloon between hot and cold water many times.
What happened? As air warms, it expands. Placing the bottle in hot water caused the air inside to expand. The only place it could go was into the balloon. By placing the bottle in cold water, the air contracted and left the balloon, causing it to shrink.
FLOATING NEEDLES
This experiment will demonstrate how the surface tension of water can keep an object afloat.
Fill a bowl with water. Carefully lay a needle on the surface of the water. It takes a steady hand to do this. If one end of the needle sinks below the surface of the water, the surface tension is broken and the needle will sink.
Once you have the needle floating on the surface of the water, add a drop of liquid soap. Watch as the needle sinks.
What happened? The needle floats because of the surface tension of the water. The soap disrupts the water molecules so that they don’t stick together so easily and the needle sinks.
ANOTHER AMAZING TRICK WITH SURFACE TENSION
Fill a small bowl with water. Sprinkle white pepper evenly over the surface of the water. Dip a toothpick into the center of the bowl. Does anything happen to the pepper?
Now place a drop of detergent onto the toothpick and dip it into the center of the bowl. The pepper scatters to the edges of the bowl.
What happened? The detergent is slippery and disrupts the surface tension of the water, pushing it away. The pepper followed the water away from the soapy toothpick in the center.
By playing with the laws of physics, kids will learn that science can be interesting and fun.
