Squash Ball Investigation
The aim of my investigation is to investigate the factors which affect
the bounce height of a squash ball.
Factors I could investigate
3. Weight of ball
4. Types of ball (dot colour)
5. Temperature of ball
I have chosen to change the height that I drop the squash ball
as the other possible variables would be unsuitable for our
Changing the hardness of the surface would be difficult to do, as it
is hard to measure the hardness of the surface.
Changing the weight of the ball would be difficult, as you can’t
accurately change the weight of the ball manually unless you buy
different weight balls, and we don’t have enough time to do it.
The types of ball would be complicated to record, as you would be
looking the dot colour and this would be hard to do in our situation
(with not enough squash balls to go around.)
The temperature would be difficult to change as there aren’t enough
water baths in the classroom and as the temperature would have to go
up quite high there is also a safety hazard.
Therefore, changing the height the ball is dropped from is the easiest
and best option to choose.
I predict that when you have a higher drop height, the ball will
Reason for Prediction
This is because when you drop the squash ball from a greater height
there is more Gravitational Potential Energy
, which will be converted
to make the ball bounce higher.
When the ball is dropped from a greater height, it will bounce higher.
When dropped from 1m, for example, it has maximum Gravitational
Potential Energy (GPE). This energy then converts to kinetic when
falling, and when it hits the floor, some more energy is lost through
compression, heat and sound. It therefore has less energy left
(elastic energy) to bounce back up and so doesn’t reach the original
height it was dropped from. For instance it may only reach 60cm from
1m. I can further predict that the ball will lose the same amount of
energy each time it falls. From the 100% of energy when it is first
dropped it may lose 40% of the energy on each bounce, and so bounces a
smaller amount each time. This can be shown in the following Sanky
diagram, however this is not vital to our investigation.
The aim of my provisional investigation is to find the best
temperature to heat the squash ball to before I drop it.
(1) (2) (2)
Drop height (cm)
In my main investigation I will use the squash balls heated to 40°C
because they are more efficient.
First I will heat up the squash balls to 40°C in a water bath. I will
then check the water bathe is the right temperature with a
thermometer. I will use tongs to pick up the ball and take it to the
surface (a table top) and lift it to a drop height o f 10-100cm in
10cm intervals. I will drop it and watch the height it bounces to
using the bottom of the ball as the measuring point against the ruler.
I will do five repeats for each height. I will be recording my results
in a table throughout the duration of the experiment. If I have any
anomalies then I will repeat the anomaly in a sixth repeat. This is to
correct the error so I get a more accurate average for later on when I
am processing my results. I will then measure the average of the
repeats for that drop height. Next, I will draw a graph to show the
average bounce height for each drop height. It will include a line of
To make it a fair test I will make the squash balls all the same
temperature for each repeat, and make sure that the squash balls are
all of the same weight (this is represented by the dot colour.
-------------------Bounce heights (cm)------------- Repeat
Drop height (m)
[IMAGE] = Anomalous result (repeat in column 6)
My evidence shows me that the higher I dropped the ball from, the
higher it bounced.
The trend (pattern) shown by my graph is that as the drop height is
doubled, the bounce height is approximately doubled as well. For
instance, when the drop height is 0.20m, the average bounce height is
4.40cm, and when the drop height is 0.40m, the average bounce height
The science that explains this trend is that when the squash ball is
dropped, the energy changes from GPE to kinetic. When the ball hits
the surface, energy is lost due to compression, sound and heat. As it
keeps bouncing, the squash ball loses more and more energy, until it
doesn’t bounce at all.
Ball weighs 0.024kg
Drop Height (m)
0.14 = 14%
0.22 = 22%
0.25 = 25%
0.24 = 24%
0.24 = 24%
0.22 = 22%
0.29 = 29%
0.29 = 29%
0.27 = 27%
0.30 = 30%
GPE = Mass x Gravity x Height (0.024 x 10 x Drop Height)
Efficiency = GPE After -:- GPE Before (Bounce -:- Drop)
My conclusion does support my prediction because I predicted that when
you have a higher drop height, the ball would bounce higher. When I
did my provisional investigation, the efficiency of the squash ball
heated to 40°C was 0.27 (or 27%) when dropped at 1m. When I did my
experiment the efficiency of the ball dropped at 1m was 0.30 (or 30%).
These results are very close to each other, even though the
efficiencies of the drops in the main experiment did not completely
comply with my prediction (there were a few anomalies.)
In the practical work, the difficult parts were keeping the squash
balls at the temperature (40°C), as you had to take the balls out the
water bath and do the drop very quickly to avoid them cooling down.
Also, measuring the bounce height accurately was difficult, you had to
make sure that you were reading the height off from the bottom of the
ball, and as it was very quick you had to make sure you got it
In the results table the measurements that look strange (anomalies)
are the fifth repetition for a drop height of 0.30m where the bounce
height was 4cm, and the fourth repetition for a drop height of 0.70m
where the bounce height was 16cm.
On the graph, the points that look strange (anomalies) are at drop
heights of 0.50m, and 0.60m. These are only slight anomalies, and only
because they lie off the line of best fit.
To measure things more accurately you could use a video camera to
measure the bounce height, by recording the drop of the squash ball,
then watching it back and pausing it on the bounce and reading off the
height it reaches. This way we can make sure we get the exact bounce
height, instead of just a rough estimate.
The reasons that the repeats are not all identical are we might have
made mistakes when reading the bounce height. It was very hard to do
as the bounce was fast and you had to be really concentrating and
accurate when you were reading off the heights.
The largest range bars are for the drop heights of 0.70m (where the
range is 5cm), and 1m (where the range is 4cm.)
To make this practical method more reliable, you could repeat the
bounces 10 times for each drop height (instead of 5). We could also
video it to check the bounce heights, make the room 40°C to keep the
ball temperature constant (controlled environment).
The strange (anomalous) results might have happened because we
couldn’t read the bounce height when it was too close to the surface.
Or because the ball cooled down over usage, the water bath could have
also cooled down. To avoid this we could stir the bath more often and
leave the squash ball in the water long enough to heat up.
Extra practical work I could do to back up my conclusion would be to
use the video camera method, to do more repeats, do the experiment
with a different types of squash ball, to do the experiment over a
different range of drop heights (1-2m), and to compare the efficiency
with different types of sports balls (golf, tennis, etc).