- We have to use the same person each time the ball is dropped because people give different forces when they release the ball.
- We have to use the same colour squash ball each time because there are different types of squash balls that give different bounces as some are softer than others
- The squash ball has to be dropped from the same height each time because the higher you drop it from the longer the ball will travel causing it to go faster making greater efficiency, also the higher you drop it from the more air resistance would take effect. This would cause the ball to hit the ground faster, so the more the ball is going to deform causing the efficiency to increase.
- The surface has to be the same because if it was bounced on a soft surface then some of the force would be absorbed so the bounce would not be as high as if it was a harder surface.
- The same person has to measure the rebound height each time because people have different reaction times so the recordings would not be as accurate.
The temperature of the ball has to be the same because the softer the ball the higher it is going to bounce.
Further detail in the effect of changing the temperature.
If the temperature is raised the air pressure inside the ball would build up. Pressure inside the ball goes up it would be more difficult for it to deform, so it would mean it wouldn’t spread so far. Energy through friction would be less so the efficiency would be higher as it would return to its original shape quicker. The temperature also affects the rubber its self. The ball is made of polymer which is easy to stretch and when it is hotter the ball deforms more as it is softer which causes more friction and for it to stretch more. This would mean the efficiency would go down.
How I am going to record my results.
I am going to heat the squash ball to the temperatures 100ºc, 75ºc, 50ºc, 25ºc and 0ºc. I am going to record each temperature three times; I am going to do the coldest temperature first then work up from there.
Equipment needed
For this experiment I will need:
- Bunsen Burner
- Beaker with 200 ml of water
- Squash Ball
- Tripod
- Gauze
- Thermometer
- Metre Stick
- Hard Surface
- Fire Proof mat
- 3 People
- Ice Cubes
Method
- Set up the equipment and heat up the water with squash ball in it.
- Then take out when it reaches the requires temperature using tongs.
- Then get one person to hold the ruler, one person to measure bounce and the other person to drop the squash ball.
- Drop the ball from 1 metre.
- Record the results into a table. Repeat three times.
To get the temperature to 0ºc we are going to put ice in the beaker before the actual test we did a preliminary experiment. We did this because we were not sure whether we should place the ball in the water before you heat it to the required temperature, or whether you heat the water and put the ball in. We found that it was better if we put the ball in the water before you heat it up so u can get the correct temperature. I f you put it in when it was heated it might not reach the temperature you require.
Prediction
I predict that the hotter the ball the more efficient it is. I think this because I think the molecules in the ball are all moving around faster and colliding more, so it would bounce higher because there is not so much friction when rebounding of the ground.
Results
Because we used 100cm stick the efficiency is exactly the same.
I have noticed that my prediction is correct. The higher the temperature of the ball the more efficient it is and the colder it is the less efficient it is.
I have drawn up a graph to see if there is any pattern. I have noticed that the graph is in a straight line.
Conclusion
I have noticed that the hotter the temperature of the squash ball the higher the rebound height. This is because when the ball is heated the polymer (the material of the ball) stretches, which means it deforms more. So it has more elasticised potential Energy when it goes back up causing it to go higher. The graph shows that the results go in a straight line. This shows that the higher the temperature the higher the efficiency.
Evaluation
The method worked reasonably well because I managed to roughly make the temperature of the ball right for every different rebound height. The results were not very accurate because the person measuring the rebound height cant make an accurate reading, as it is too quick, also we were unable to make sure that the temperature of the ball was exactly the same for each bounce. This was because we were not sure how quickly the temperature of the ball would drop. There were no anomalous results as most of the recordings were near enough the same. If I were to do the experiment again I would use three balls and reheat one at a time so I could be certain that the temperature is as accurate as possible. I would then drop one ball then drop the other heated ball etc.. This would mean the ball would be very near to the temperature each time.
If I was to do this experiment again then I would change the experiment by keeping the same temperature but dropping the ball from different heights. I would then be able to make an accurate conclusion for the efficiency of a squash ball.