Main Plan
I am going to use what I found out in the preliminary experiment to help improve this one. I am going to find out what the relationship between the height a ball is dropped from and the height it bounces back up to is.
Equipment : A rubber bouncy ball
Tape measure
Pencil
Cellotape
Plan : I am going to drop the bouncy ball from five different heights ; 200cm, 150cm, 100cm, 50cm and 25cm. They are quite high so I can read off an accurate result. I will tape a tape measure securely to a wall so that it will be kept steady. I will get a friend to drop the ball from each height so that I can record how high the ball bounces back up to in a table. I will do the same experiment three times so that I can get an average of each height and I will record all my findings in a table.
Safety : I will secure an area around the metre sticks that no-one else, apart from me, will be allowed in. So that if the ball bounces off at the wrong angle no-one will be hurt. I will make sure that I bounce the ball on a smooth surface so that the ball will bounce straight back up to me.
Fair test :To keep the experiment a fair test my only variable will be the height that the ball is dropped from. I will use the same ball for each experiment because another ball could produce a different result and I will have the same person dropping the ball each time.
Prediction : I predict that the ball won’t bounce back up to it’s original height and that the height I record for the bounce will be lower. I predict this because the ball will have lost some of it’s energy during it’s journey and won’t have enough to get back to it’s starting height.
Scientific evidence :Before a ball is dropped it has potential energy because it isn’t moving but when the ball is dropped and is moving through the air it has kinetic energy. The ball has the most kinetic energy just before it hits the floor because it has been building it up. When the ball hits the ground it loses energy through sound and heat and this is why it doesn’t bounce up to it’s original height.
Diagram :
Table of results :
Averages : 200cm- 142+157+155 = 151.3cm
3
150cm- 118+119+117 =118cm
3
100cm- 77+78+81 = 78.66cm
3
50cm- 36+41+41 = 39.3cm
3
25cm- 15+16+17 =16cm
3
Analysis
If I take the bounce height away from the drop height I will be able to discover if the height of the drop affects the height of the bounce or if the difference stays the same.
Drop height(cm) Bounce height(cm) Difference(cm)
200 151.3 48.7
150 118 32
100 78.66 21.34
50 39.3 10.67
25 16 9
From this table I can see that if you raise the drop height the bounce height of the ball is also raised and the difference raises as well. I will now put my results in a graph.
From these results I can see that the difference between the drop height and the bounce height decreases when the drop height decreases. This is because the higher the ball is dropped from the more potential energy it has so that when it drops it gains more kinetic energy. With more kinetic energy it has more power to bounce back up. As it hits the floor the ball compresses and loses energy through heat and sound. The ball then decompresses, pushing against the floor and forces the ball up again.
The results I collected do support my prediction because on all the results the ball didn’t bounce back back up to it’s original height. You can tell this from my graph.
Evaluation
My prediction was correct because the bounce height was smaller when the drop height was smaller, this was because there was less potential energy. The bounce height was smaller then the drop height because energy was lost in heat and sound when the ball hits the ground.
I did have two anomalies and they are circled in red on my table. On each one i thought it looked strange so I recorded them again and got a more expected result. I probably got these anomalies because the ball bounced at a different angle or it was dropped differently. I excluded the anomalies when doing the averages and used the new results when doing the graph.
The results I got were quite accurate apart from the anomalies because I did the experiment three times and the results were all quite close together.
If I were to do this experiment again with any equipment I would use a camera to film the ball bouncing and then I could calculate where the ball bounced to before it fell back down. This would make the experiment more accurate.
The experiment was as much of a fair test as I could get it but it probably could of been fairer. I used the same ball on the same surface but sometimes the ball wasn’t dropped from the same height each time so it could’ve been a few centimetres different. Also on some occasions the ball could’ve bounced off at a different angle.
In conclusion the drop height does effect the bounce height so that the higher the drop height, the higher the bounce height.
