K.E. = ½ mv²
From the formula, we can derive that the heavier the ball and the faster it is moving, the greater the impact there is on the ground.
Another way of showing the loss of heat and the energy consisted in a ball is a sankey diagram. This is shown below.
Factors affecting the bounce of a ball
There are many factors of which need to be considered whilst investigating one of them. Below is a list of factors that could affect the bounce of a ball.
- Height of which it is dropped at
- Weight of ball
- Type of ball – material
- Surface area of ball – size
- Type of surface of the ground
Variables
DEPENDENT: - height of rebound
INDEPENDENT: - size of ball
- surface of ground
- material of ball
- height of dropping the ball
- weight of ball
CONTROL: - pressure of ball
Prediction
I predict that the height, of which the ball is dropped at, is directly proportional to the height of its rebound. This tells us that if the height of the ball it is dropped at increases, the height of its rebound will also increase, provided the graph shows that a straight line is produced which goes through 0. This can be showed in the sketch below.
y
- x
Hypothesis
To extend my prediction, I need to produce scientific reasons to prove that my prediction should be correct.
Referring to the background knowledge, I found out that the amount of work put into the ball, its potential energy, must be equal to the amount of work the object can do, its kinetic energy. In other words, the higher the ball that it is dropped at, the higher it will bounce back up.
Preliminary Work
Method
Because of lack of time, the plan was to start recording measurements at 200cm. We started to take measurements starting from 100cm. We dropped the tennis ball at 100cm and we carefully saw what the height of the rebound was. Three repetitions were taken, using lengths of 90cm, 80cm, 70cm, 60cm, 50cm, 40cm, 30cm and 20cm to gain accurate results.
Results
After carrying out the preliminary experiment, I have decided to use a tennis ball for the final experiment as I had gained good results. Also another reason for using a tennis ball is because if I had used a larger ball, I would not be able to record the measurements, due to its height. This also applies if I had used a smaller ball because it would travel too fast and it would be difficult to take down the rebound distances. I have decided to use the same measurements, except I am not going to consider using 20cm due to the height of the ball.
Range
I will be using a range of 30cm – 100cm, going in steps of 10cm each time. I have chosen this range because it is easier to acquire results in the laboratory and good results can be gained.
Reference
Below are resources I have used to find information on the effect of bounce on balls.
Apparatus
Diagram
Method
- Set up the experiment as shown in the diagram.
- Drop the tennis ball at 100cm and watch carefully at the distance it arrives at its rebound.
- Repeat this set of results at least three times to gain accuracy.
- Drop the ball at 90cm and carefully note down the measurements.
- Carry on with the procedure until there are three sets of results for each height the ball is dropped at.
- Record the results in a table.
- Work out the average rebound height and a line graph would be suitable because the results are continuous.
OBTAINING AND ANALYSING EVIDENCE
Results
Graph
Below is a graph of the rebound height of a tennis ball.
Conclusion
From the graph, we can see that there is some proportionality between the height of which the ball is dropped at and the rebound height. However, we can not say that there is direct proportionality because the line does not go through 0.
We can find a gradient from the graph by using the equation y = mx + c. The gradient will show the energy relationship between the two different heights.
Equation: y = mx + c
M=25
C=13.5
So: gradient = 25/13.5
= 1.85
We can also find the gravitational potential energy by using the formula,
G.P.E = Weight * Height
G.P.E = 6 * 6.5
G.P.E = 39 Joules
Therefore, the gravitational potential energy is 39 Joules and we can derive that the smaller the weight and height of position of the ball, the smaller the potential energy.
The results support my prediction. I mentioned in my prediction that if the height of the ball it is dropped at increases, the height of its rebound will also increase. This is due to the amount of work that is put into the ball. Its potential energy must be equal to the amount of work the object can do, which is its kinetic energy. However, the line did not show that the two heights are directly proportional to each other. This could result in an error during the investigation.
EVALUATING
The plan of the experiment had worked well as I had gained good results. However, when the actual experiment was undertaken, I gained one anomalous result. I suggest that an error had taken place and I think that the measurement taken was not looked at carefully. To solve this, we could use a device that can capture the height measurement, which will make it easier to record.
Some improvements could be made to this investigation by adding a few modifications.
Firstly, I would use a larger ball and compare the energy between a larger ball and a tennis ball. I could, however, use a smaller ball than a tennis ball and also compare the energy relationship between the three balls.
There are other possible ways that could be used to take measurements for the rebound height.
We used an ultrasound ranger, which detects the height of which the ball is bounced back up. However, the graph that produced the results was not very accurate and several errors were made, such as many different points were produced and it was extremely difficult to make out the rebound height.
We also used a digital camera, which is a good thing to use; however, we could not zoom in to find the measurements.
To extend this investigation, I have decided to use a digital video camera because we can take a movie of the ball being dropped and the rebound height and zoom in to find the measurements. This would be a more accurate way of recording the rebound heights due to the expansion of the movie clip.
