Height of Drop
As seen in the preliminary work, the higher the height at which the ball is dropped from, the higher it will bounce back. This is because as the ball travels down, it has more time to gather speed if dropped from a higher height due to the acceleration of gravity and this will increase the height at which the ball bounces back up as the ball will bounce up with a greater force. For all experimenting, the height will be kept at a constant i.e. if I was investigating the bounce of ball heated at 300C I would test each bounce at the same height to ensure the result is fair.
Material of Ball
This variable affects the bounce of a ball in a number of ways:
a) According to what material it is made of, its molecules may melt and reduce the height of the bounce earlier or later than other balls.
b) Some materials may be better insulators of heat which would mean that they would bounce higher than those balls made of materials which are poor insulators as they will not loose the heat energy as quickly.
c) Some materials may have a molecular structure that allows a lot of space for air molecules which would result in an increase of air pressure within the ball affecting its bounce back height (the higher the air pressure, the higher the bounce back height).
To have fairness in the testing of balls, I will use the same ball each time for any kind of testing ensuring that the material of the ball is not different giving accurate, reliable results. To be very fair, a different ball made of the same material should be used each time as using the same ball which has been heated several times may affect the results slightly.
Mass of Ball and acceleration
The heavier an object is, the faster its acceleration rate. This can be shown using the equation F=ma where m is the mass of the object and is the acceleration rate. To understand why the mass of an object affects the acceleration rate, when we rearrange the formula to make a (acceleration) the subject, we get a=F/m, force divided by mass gives acceleration. Because F is constant, this means that the bigger m is (or the mass) of an object, the bigger the acceleration is. Knowing that the mass of the ball will affect the results, I will be using the same ball (of the same mass) to ensure that its acceleration rate will be constant throughout the experiment.
Diameter of Ball
A larger ball with a larger diameter will have a bigger surface area meaning that when it hits the floor, more of its area will be in contact with floor at impact and this will affect its bounce back height. For this reason, to make the test fair, the same sized ball with the same diameter will be used.
Type of Surface
Different surfaces have different smoothness and changing the surface half way during the experiment will make the test unfair as some surfaces according to their smoothness will allow a nice, neat bounce whereas other surfaces will alter the bounce due to indentation in the surface and bumps etc. To make the test fair, all testing will be done on a bench surface throughout the experimenting procedure.
Angle of Surface
The angle of the surface at which the ball is bounced on will affect how it bounces back up and how far too. To overcome this, a surface, which is horizontally straight, will be chosen to experiment on. This same surface will then be used so that there will not be any change in its angle making the test fair.
Angle which Ball is dropped at
Changing the angle at which the ball is dropped half way through the experiment would make the results unfair again as it would affect how the ball bounces back up (at what height). For my experimenting, I will simply drop the ball perpendicular to the hard surface each time ensuring that this is the angle at which it is always dropped throughout the experiment.
Air Resistance
As the squash ball moves through the air, the air in front of it experiences a rise in air pressure and pushes the ball in the opposite direction causing it to slow down.
Temperature of ball
The temperature of the ball can change; the molecules inside the ball can either heat up or cool down. As the temperature rises the molecules gain more energy and bounce off of one another and off of the surface of the ball more rapidly causing a much higher bounce. As the temperature decreases the molecules lose the energy and bounce off of each other and the surface more slowly causing a lower bounce. I will investigate this.
Force and Height Dropped
The height the ball is dropped from and the force has an impact on the height it bounces back on. The more force is placed on the ball the higher the ball will bounce.
Method
I will place the squash ball in a bag; I will then place a thermometer in the water and heat/cool the water up/down to the needed temperature. I will leave the ball in the beaker for 3mins to allow it to heat up. Once it is at the desired temperature I will let the ball freefall from 1meter. I will then measure and record the height of the first bounce only.
I will repeat the experiment five times.
Hypothesis
I think that as the ball heats up the bounce will be higher, as it cools down the bounce will be lower. I think that this is the case because of the atoms of air inside the squash ball. As the temperature increases the atoms will collide more regularly, this is the case in chemical reactions as raising the temperature makes the particles move faster and lowering the temperature causes them to decrease in speed. This means that more particles collide with each other per second.
The rate of the reaction increases.
Also, if the particles are traveling faster, more of them which will have the required activation energy for reaction to occur.
As a general guide:
- Raising the temperature of a reaction by 10°C will double the rate of the reaction.
- The gradient of a graph of rate of reaction against temperature will be twice as steep.
A diagram to show the molecules inside the ball when heated and cooled.
Result
Mass of ball = 25.42g
Room Temperature = 18 ºC
The graph of the average results is over the page.
The results are what I expected them to be, the higher the temperature of the ball the higher the bounce, my hypothesis was correct. According to my results if the ball had been 80ºC then the average result would be a lot higher.
Evaluation
If I had measured the second bounce I would have found a difference as the energy would have been lost to sound and through the ground.
As the temperature raises the speed increases as does the pressure causing a greater bounce. The ball becomes deformed as it hits the ground as it changes direction. If I had time I would have done a second experiment and changed the height it was dropped from. I would expect the height of the first bounce to increase as I increased the height it freefall from. I also could have changed the mass of the ball while I changed the temperature to see if both have an effect on the bounce.
I believe the experiment was a success as I have gained no anonymous results in the table above.