Bouncing Ball Experiment

Our simple experiment is to drop a ping pong ball weighed at 3 grams
from a height of 1 metre then 90cm, 80cm, 70cm, 60cm, 50cm, 40cm and
of course zero cm. From dropping the ball we can see how high the ball
will bounce to after having a loss or gain of energy due to sound or
movement of the ball as it hits a hard surface. I will drop the ball 3
times altogether, on the second bounce I will look specifically at the
point it is likely to bounce to so the results will be more accurate.
After doing this three times I will then take an average to make it
more accurate. This will then even out any freak results, which occur.
While completing the experiment I will be taking note of the bounce
height of the ping-pong ball in a table of results. I will also make a
table of results for the amount of energy lost/gained.

We are trying to find out what will happen to the energy at potential
and kinetic points in the ball's bounce. We will be investigating what
type of energy is lost or gained, and whether or not a factor that is
changed in the investigation affects the results such as a change of
surface. Prior to this investigation we did preliminary work on a
computer program where you pressed go on the computer so that it
dropped the ball and it would automatically stop at the highest point
of its bounce. You could select the measurement you dropped the ball
from and it gave very accurate results.

Diagram

[IMAGE]

Hypothesis

I predict when doing this experiment that the higher we drop the ball
from, the higher the ball will bounce to, because more potential
energy is gained from a greater height and therefore it will have more
kinetic energy at the surface and may bounce higher but energy is
still lost to heat, movement, sound and speed, therefore the ball will
never reach its original height that it was dropped from, when no
pressure is on the dropping of the ball. I think this will happen
because the potential energy is being converted to kinetic energy as
it slows down and hit's the surface. As I said some of the energy is
converted also into heat, sound and speed as it leaves the surface,
which it bounces from, because the energy has been transferred. It
will now finish less gravitational than it started therefore it will
never gain more energy than it started with and will never reach the
height it started from after it has bounced! I also predict there will
be no bounce height at zero cm because it is on the surface and it is
not possible to drop it therefore it cannot bounce!

If we were in a different situation using a ball, which is not hollow,
I predict that the ball would bounce lower than a ping-pong ball when
dropped from the same height. I think this because, the ping-pong ball
cannot store energy and therefore it will waste more energy on heat
sound and will bounce higher. The ball that is not hollow will do the
opposite.

As shown in this diagram below.

[IMAGE]

Use the same ball for every part of the experiment because using a
different weight or shaped would mean we would have very in-accurate
results because the ball could bounce higher/lower than our 3-gram
ping-pong ball. If we were to use a harder ball e.g: cricket ball,
after the bounce the ball would not recover as much of its potential
energy as a ping-pong ball.

The bounce height of the ball will always be read from the bottom of
the marking of the ball never the top or side etc. In the room that we
are doing the experiment the temperature will try to be kept the same.

The ruler used to measure the drop/bounce height will be kept held in
place by a clamp stand and touching the surface at all times. It will
also be held tightly by the clamp stand for extra security and
accuracy. The reason we are not going below 40cm on the measuring
ruler is because anything below 40 cm is too low to get an accurate
result from. It isn't possible to get your eyes down low enough to
read an reliable result. Zero is an exception as I mentioned in my
hypothesis. Apparatus/equipment will be kept the same constantly. The
only factor that we will be changing is the height at which we drop
the ping-pong ball.

Method

1: Make sure you have followed all the safety rules and put the entire
apparatus together ready to start the experiment.

2: You need two people, one to drop the ball and one to read the
marking. So the person dropping the ball stands with the ball held at
100 cm on the ruler, when the second person is ready, the ball is
dropped. When it bounces to the highest point of its bounce they read
the number on the ruler from the bottom of the ball. Record this in a
results table.

3: Repeat step 2 twice, recording the results and then take an average
of the three.

4: Repeat step 2 but this time drop it from 90cm three times then
80cm, 70cm, 60cm, 50cm, 40cm and 0cm. Doing each of these heights
three times and take an average.

5: Once you have finished the experiment pack away your apparatus.

Results table

Table of results to show: The loss of energy

Drop height (m)

Average bounce height (m)

Initial P.E

(j)

Final P.E

(j)

Loss of energy

1.0

0.67

0.003

0.00201

0.00099

0.9

0.58

0.003

0.001566

0.001434

0.8

0.53

0.003

0.001272

0.001728

0.7

0.53

0.003

0.001113

0.001887

0.6

0.44

0.003

0.000792

0.002208

0.5

0.37

0.003

0.000555

0.002445

0.4

0.29

0.003

0.000348

0.002652

0.0

0.00

0.003

0.00

0.003

Analysis

From my results and graphs I noticed that as I increase the drop
height of the ball, the bounce height would also increase. This is
what I predicted in my hypothesis, because more potential energy is
gained from a greater height. You can also notice this in my first
graph because it is a line which always goes up, never down. Apart
from the odd result. In the second results table showing the loss of
energy, the energy loss decreases as the height decreases because
there was less potential energy to start with. So there is less energy
to loose.

I also noticed that the result for the bounce height was always in a
boundary of 20-40 cm difference from the original drop height. This is
explained partly in the diagram below.

[IMAGE]

At mass (m) and at height (h), the ball is at 100cm above the ground,
its p.e = mgh. When the ball drops, Its velocity increases and it
gains k.e, at the expense of its p.e. At the bounce the potential
energy is recovered if it is bouncy. A hard ball would not therefore
it would not bounce very high at all. If it starts from rest and air
resistance is negligible, its velocity (V) on reaching the ground is
given by:

v2 = u2 + 2as = 0 + 2gh = 2gh

Or as it reaches the ground:

k.e = ½ mv2 = ½ mx 2gh =mgh

Loss of p.e = gain of k.e

We can now see from doing this experiment that it a great example of
the principle of the conserving of energy.

ENERGY IS NEVER DESTROYED, ONLY CHANGED FROM ONE FORM TO ANOTHER.

I can now refer back to my hypothesis, I can see that my prediction
was correct. That the higher the drop height of a ping-pong ball the
higher the bounce height! I have also proved that more potential
energy is gained from a greater height and that the ball will NEVER
bounce to the original drop height because energy is wasted to sound
heat movement etc.

Evaluation

While gaining my results from this investigation we made sure we
observed carefully for any mistakes when dropping the ball. After
every three we checked that the ruler had not moved

The experiment was carried out with as much accuracy as possible!

I think we took plenty of measurements to suit our plan, so that we
provided reliable and precise results.

I am happy with the results we have gained from this experiment, I
think it was a good experiment but I do not think it was not very
accurate. I think this because the ball not of been dropped from
exactly the correct point each time. It was also very easy to read the
measurement incorrectly as it Is mid air which makes it very difficult
to read at all never mind the bottom of the ball. This in accuracy
will of affected my results. I do not think this procedure was very
suitable for this experiment because it was very hard to read the
measurements accurately. To solve this problem I think perhaps we
could use a light sensor connected to a computer, so that when the
ball bounces to its highest point it will be recorded very accurately
but this could still prove inaccurate because there is no solution to
how we can drop the ball accurately.

At 70 cm, I noticed an odd result as marked on my graph previously
because at 100cm, 90cm and 80cm there was a clear pattern, the higher
the drop height then the higher the bounce height of the ball. Until
70cm because at this point the average bounce height was 53.2cm which
is higher than the result for 80cm which was 52.5cm. I think this
happened because maybe the ball was dropped from too high by accident,
the measurement reading was taken in accurately. There were no other
odd results.

Over all I think it was quite a good experiment to show how energy is
wasted/gained and conserved.

I think that when we did this experiment on the computer program it
was very accurate compared to this method because it was drop from a
very precise height and automatically stopped at the highest point!