Everything Kids' Magical Science Experiments Book Read Online Free PDF Page B

forth. You are truly “burning the candle at both ends.”
    Science Quote

    â€œThe universe is full of magical things, patiently waiting for our wits to grow sharper.”
— Eden Philpotts, English science-fiction writer
Questions for the Scientist
Why might it be important to light the ends of the candle one at a time instead of at the same time?
Imagine that you could place the candle high enough above the table that it would not touch the table if it tipped. How might the experiment change?
How might your results change if the candle were not uniform in shape, that is, thicker on one end, thinner on the other?
Science Fair: More Bounce to the Ounce
    As you have probably noticed, some balls bounce better than others. For example, a football doesn't bounce all that high, but a golf ball will often bounce several times before coming to rest. These balls bounce the way they do because of what they are made of. But if you were to put some of the balls together, you would be amazed by the results.
    Question: Which balls bounce best?
Experiment Overview
    In this experiment, you will begin by dropping several balls of your choice, one at a time, from a predetermined height. You will measure their bounce height and record it in a data table. Then you will begin placing one ball on top of another and repeating the drops. This time, the heights to which the top ball bounces may surprise you. Your goal will be to determine which combination of balls produces the most impressive bounce of all.
Science Concept
    When you drop a ball on the ground, some of its kinetic energy is transferred into the ground. The energy that remains is what makes the ball bounce back into the air. Some balls, such as golf balls and the super bouncy balls, retain most of the energy and bounce back to almost the same height from which they were dropped. However, other balls, such as bowling balls (which should never be dropped on the ground), lose almost all of their energy and if they do bounce back up, don't go very high in the air.
    However, when you place one ball on top of another, some of the bottom ball's energy is transferred into the top ball after the bounce, which can make the top ball appear to fly into the air. The heavier the bottom ball is compared to the top ball, the greater the effect.
    Did You Know?

    The term that describes how high a ball bounces when dropped is coefficient of restitution . It is found by comparing the bounce height to the drop height and taking the square root of the result.
Materials
Several round balls. Some possibilities are:— Basketball— Tennis ball— Rubber bouncy ball— Playground ball— Golf ball— Baseball
Measuring tape
Helper
Open space for testing
Procedure
Identify at least three balls you would like to use in the experiment.
Hold your arms straight out in front of you and have your helper measure their height above the ground. This will be the drop height for each of your trials.
With your helper ready to measure the bounce height, drop each ball by holding your arms directly in front of you and letting go of the ball.
Record the height to which each ball bounces.
Choose different pairings of balls to test. For example, you might select a tennis ball on top of a basketball.
Carefully hold the two balls at the same height as before with the one you chose to be on top sitting squarely on top of the bottom ball.
Drop the balls and have your helper measure the bounce height of the top ball. To double check, repeat this step until you feel confident in your measurement.
Repeat steps 5–7 as many times as you like. Be sure to try heavier balls on top of lighter balls as well.
Questions for the Scientist
Was there a difference in the results between placing a light ball on top of a heavy ball and placing a heavy ball on top of a light ball? Why do you think this difference exists?
In looking at your results, which factor do you think has the biggest impact on the bounce