Apparatus
· 1 Tub of sand
· 1 Ruler
· 1 Metal Ball Bearing (63.7g)
· 1 Metre Ruler
Method
1. Set up the apparatus (as shown in the diagram)
2. Lift the Ball Bearing to a height of 10cm and drop into the tub of sand.
3. Place the end of the ruler at one edge of the crater and measure to the other side. This gives the width of the crater.
4. Repeat steps 2 and 3 at 10cm intervals (20cm, 30cm etc) up to 100cm.
5. Repeat 3 times
6. Record in Results Table
Fair Test?
The factors, which would affect the size of a crater, are:
· The mass of the ball bearing because if it was heavier then the amount of G.P.E it has would increase due to the fact that the formula for G.P.E is Mass x gravity x height. So if the mass of the ball bearing were greater the G.P.E would be greater so therefore the K.E would be higher so the crater would be larger.
· The size of the ball bearing because the bigger the ball bearing the more of it there is to hit the sand, therefore the crater it makes will be not necessarily deeper but it will be wider. Because I am measuring the width of the crater I need to keep the size of the ball bearing the same.
· The material the ball bearing is made of because that it will push the sand out of the way in different ways.
· The depth of the sand
To make this experiment fair I am going to keep all of these constant.
In order to make this experiment as fair as possible I am going to vary the height of the ball bearings at 10cm intervals. I am going to use the same ball bearing and the same depth of sand throughout in order to make this a controlled, fair test.
Prediction
I predict that, in this experiment, the higher the ball bearing the greater the width of the crater. The scientific knowledge that supports this is that the Ball Bearing has Gravitational Potential Energy (Mxgxh=G.P.E.) and as it falls the Gravitational Potential Energy converts into kinetic energy (1/2MxV =K.E.). The pull of gravity on Earth is 9.81 Newtons/kg or 9.8 Metres/sec .The higher the ball bearing falls from the more Gravitational Potential Energy it has so the more kinetic energy it gains. When it hits the sand the kinetic energy is transferred into the sand as heat and more kinetic energy moving the sand out of the way. So therefore the more energy the ball bearing has when it hits the sand the wider the crater it should make.
Preliminary work
For my preliminary work I decided to test my experiment at the two extremes. These will be the smallest height I intend to drop the ball bearing from and the greatest height I intend to drop it from.
These are; 10cm and 100cm
The results I got were:
My preliminary work has been positive because I have found that 10cm is a sufficient height to drop the ball bearing from to give me a decent result, the crater is not so small that I cannot read its width easily. I have also found that 100cm is not too high to be accurate with where the ball will land and it does not splash too much sand out of the tray.
This preliminary work has shown me that I don’t need to make any adjustments to my original method for my final experiment.
Results
Width of crater (mm)
On my first set of readings I had a few anomalous results that I have highlighted in red on my chart, I have repeated these results and written then next to the original ones. I then took the average from the repeated results.
At first I couldn’t tell if the line on my graph was a curve or a straight line. To find out if my graph would level off I tried dropping the ball bearing from 2 metres, twice my maximum height of 1 metre. So if my graph were a straight line it would be a very big crater. However the crater was only 95mm, which is only 10mm bigger than my result from dropping the ball bearing from 1 metre. This shows that the graph would eventually level off. This means that the graph is a gentle curve.
