Investigation on how high a squash ball bounces.

Investigation on how high a squash ball bounces

I am going to investigate the different factors effecting how high a squash ball bounces. The variables that could have an effect are:

The height which the ball is dropped from
How hard the ball is thrown down
The surface the ball land on
The mass of the squash ball
The temperature of the squash ball
The type of material the squash ball is made from

Although all of these variables will have an effect on the results I get, I will only be able to measure the height from which the ball is dropped from and the temperature of the ball. This is because all of the other variables would not produce a suitable graph, for example I could not plot a graph, which says different types of surfaces at the bottom and how high the squash ball bounces at the side. This is because there is no increasing number to the surfaces it would be things like concrete, carpet and wood floor.

While the ball is in your hand it has potential energy. As soon as you let the ball go gravity has a bigger effect on it so it will be pulled down to the ground. The potential energy will then be converted into kinetic energy. Air resistance slows the ball down; this means that the energy is not 100% efficient. If it was the ball would bounce back up to the same height each time. Just before impact (just before the ball hits the floor) the kinetic energy is a lot greater, as most of the potential energy has been converted. When the ball hits the ground there is maximum kinetic energy and no more potential energy. As the floor is solid it does not absorb much energy, strain energy from the ball changing shape makes the ball bounce back up. If there were no strain energy from the ball being squashed, it would not bounce back up. When the ball bounces back up off the ground the kinetic energy gets converted into back potential energy. Throughout this process energy is lost through air resistance, sound, heat and through the ball changing shape, this is why the ball does not keep bouncing at the same height each time (why it loses height).

There are two ways which temperature can have an effect on how high the squash ball bounces. One is when rubber is heated the rubber chains lengthen. This means that they are more flexible so that the rubber can bounce back quicker, this is why a squash ball, which is quite warm, bounces higher than a cooler one. The second way which temperature has an effect is when a squash ball gets hot the air inside has greater pressure, which means that more particles hit the side of the ball per second. So, the particles have more energy and ...

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We did a preliminary experiment to get an idea of suitable heights to drop the squash ball from. We did this by dropping a squash ball from heights going up in 25cm from 50cm to 300cm. We will then choose about 6 heights to drop the ball from for the final experiment.

Here are the results:

After doing this experiment we decided to use 6 of these heights: 50, 100, 150, 200, 250 and 300 cm. We then did an experiment to see how much the temperature had an effect on the height the squash ball bounces. To do this we placed the squash ball with the test tube holders in water at the required temperature for 2 minutes and then let the ball go, from 1 metre each time and then we measured how high it bounced. Here are my results:

My graph which shows me how high the ball bounces when the temperature increases is a steady, straight line. This tells me that as the temperature increases the height the ball bounces also increases. This could effect my results because the ball gets hot the more times it is drop, so the results I do near the end could be higher. The ball should be first dropped at about room temperature, if the temperature increases to 34°C the change in the height of the bounce will be about 5cm. Although, It is not very likely that the temperature will increase by more than 10°C, even if it did I would be able to feel the change.

Prediction:

I predict that the higher the ball is dropped from the higher the ball will bounce. I think that doubling the height in which the ball is dropped from will make how high the ball bounces back up double. This is because when measuring how much potential energy you have got we use the equation: PE= MGH

Potential energy (J) = Mass (kg) x force due to gravity (n/kg) x height (m)

So if you double the height and the mass and force due to gravity stay the same (which they do) the amount potential energy must double to balance the equation. So, the more potential energy an object has the more kinetic energy it has, making it bounce higher.

There are a lot of energy changes while the ball is falling to the ground, most of the energy is lost due to heat, sound and from the ball changing shape. This is why the ball does not bounce back up to the same height each time.

Method:

We will drop the squash ball (weighing 24.2g) from 6 heights, these are: 50, 100, 150, 200, 250 and 300cm. We will measure these heights by using two meter sticks and a tape measure, these will be placed up a flight of stairs. We will do three experiments for each height and take an average at the end. Using this average we will plot a graph and draw on a line of best fit.

We will drop the ball from the top of the chosen height (so the bottom of the squash ball is over the height) and hold it using test tube holders. This stops any body heat from transferring to the squash ball, making it warmer. The method we are using is not that accurate, so we’ll have to look closely and then point to the nearest height on the meter stick.

Equipment:

Tape measure

Two Meter sticks

1 Squash ball

Test tube holders

Here are my results:

Conclusion:

In our experiment we did get one odd result (highlighted in red), this could possibly be because we had done11 previous experiments before and the ball got hotter. I did not count this result in the average. My graph shows that the average result from dropping the ball from 250cm is quite a bit away from the line of best fit. This could mean that the ball did heat up quite a bit, because the experiments for the 300cm drop were done on a different day so the ball would of had chance to cool down.

As we measured the height of the bounce from the top of the ball the graph does not go through 0. I drew on a line of best fit to show what it would of looked like if it went through 0 (in purple) and my results look quite accurate. Apart from the result for 250cm being out my graph is in a nice straight line, this shows me that the height the ball was dropped from and the height the ball bounced to are proportional (If one doubles so does the other).

My graph shows me that if the height the ball is dropped from doubles, so does the height the ball bounces, which agrees with my prediction. For example:

When the ball is dropped from 50cm, the ball bounces to 13cm. When the height is doubled and is dropped from 100cm, the ball bounces to 26cm. This is exactly double.

When the ball is dropped from 125cm, the ball bounces to 32cm. When the height is doubled and is dropped from 250cm, the ball bounces to 60cm. This is almost proportional. This proves that my prediction was correct.

But, when I dropped the ball from 150cm, the ball bounced to 38cm. When the height was doubled to 300cm, the ball bounced to 84cm. This is 8cm out, a possible reason for this could be because I was near the end of the experiment and the ball had been dropped a few times, causing it to get hot and bounce slightly higher.

PE=MGH- Because the mass (24.2g) and force due to gravity stays the same (9.8 N/kg) and the height is doubled, the amount of potential energy must double to balance the equation.

From using this equation I can see how much potential energy the ball has from each height it has dropped from. To do this I do this sum:

PE= 24.2 (mass) x 9.8 (force due to gravity) x height

So the total potential energy for a ball dropped from 50cm would be:

24.2 x 9.8 x 50 = 11858 J

To work out the energy efficiency you need to do this sum:

Average bounce

Height ball is dropped from

Multiplied by 100 (to convert to %)

So, the efficiency for a ball dropped from 50cm would be:

7.7 divided by 50 = 0.154

0.154x100=15.4

Or 15%

The energy loss would be:

100-15= 85

Evaluation:

My results are very accurate, my graph tells me this because they all (apart from one) are very close to the line of best fit. Most of my results agree with my conclusion because as I doubled the height the ball was dropped from the height the ball bounced to doubled (or nearly doubled), apart from the last height (300cm). The height which was taken when the ball was dropped from 250cm was odd, this was probably because we had done 9 previous experiments before this one and the ball got warmer, giving the particles more energy, making it bounce higher. The rubber structure would also have been more spaced out so that it had more strain energy, so that it could bounce higher.

I thought that this method was not very accurate. The main problem we had with it was looking what height the ball actually went up to on the meter stick because it happens quickly. Another problem was trying to keep the ball at the same temperature; this is very hard when you need to keep dropping the ball because you cannot help it when the ball gets warmer.

If I did this experiment again I would use a camera and take a photograph of each height the ball was dropped from, this would make the image still so that it would be easier to read instead of guessing. I would also put the squash ball in water baths to keep the temperature of it the same at all times.