FAIR TESTS:
- The factors that will affect the depth of penetration of a pile driver are the mass and the height. I am going to investigate the relationship between the height and the depth of penetration of a pile driver, during the experiment, I will keep the mass the same. In the experiment, I am going to use the object with the mass of 200g instead of 50g. This is because when they both dropped in the same height, the depth the rod get into the sand by the 200g object will be bigger than the 50g object, therefore it’s more accurate to use the object with the bigger mass especially when the height is small.
For instance, when the height from the platform to the object is small, you can
easily read the depth more accurately by using 200g objects.
- During the whole experiment, I am going to use, the same object--- the brass mass instead of a tennis ball or plastic.
I am not going to use tennis ball, because when the ball touch the platform, it will bounce up so the gravitational potential energy will change to kinetic energy, the energy can’t get to the platform. As the result, I am not going to investigate.
Why I am not going to choose plastic, because………………..
- I will choose the height between 50cm-5cm. Each time, I will vary every 5cm height.
SAFTY:
For my safety, I am going to wear goggles, also I will be careful with the ball when it drops down.
APPARATUS:
Rod and platform put on together
A Cotton roll
A can of sand
A 200g bass mass.
A 50cm ruler with 0.2cm of scale division
An electrical balance
A goggle
Two clams: one for the ruler, one for the cotton rolls
THE PRELIMINARY EXPERIMENT:
In the preliminary experiment, I going to work out either the maximum height (50cm) or the minimum height (5 cm) or the height from an object to the plat form, if it is suitable?
After the experiment, I found that the maximum height 50cm is too high, as the brass will fall onto the floor; also it is too dangerous, so I will use the maximum height 30cm.
Obtaining evidence:
This shows the height of the 200g brass from the platform and the depth of the rob get into the sand.
Analysing and concluding:
The graph shows that the depth of the rod into the sand increases as the height from the brass to the platform increases. The gradient increases as the height from the brass to the platform increases. By this, it means a small change in the depth of the rod into the sand when the height from the brass to the platform is small and a big change in the depth of the rod into the sand when the height from the brass to the platform is big.
The results show that some of the prediction in the plan is right, some of them are wrong. I predicted that if the height from an objected increased, the depth of penetration of a pile driver into the sand increased. This is right as the table and the graph showed.
However, the second prediction I made was wrong.
In the predictions, I said the relation between the depths of the rod into the sand is directly proportion to the height from an object to the plat form. But the graph shows that small change in the depth (from the rod into the sand) when the height is small. This is because the work done of the rod is equal to the work done of the brass, as energy can’t disappear when it transfers.
Work done= force* distance moved in the force direction
Work done of the brass= weight* height from the platform
As the weight is kept the same, as the height increases, the work done of the brass increases directional proportion to the height.
The work sine to the rod=force*height it moves, as the work done increases, the force also increases as a large force on the rod by the increasing of the height between the brass and the plat form.
This makes the height decrease indirectly to the work done of the rod.
To sum up, the small change in height, the big change in the depth, the big change in height, the small change in the depth.
So the graph of the relation between the depth rod into the sand and the height from the brass to the platform will be show below:
EVALUATING:
Difficulties:
During the experiment, I have kept the mass of the brass the same. However, during the experiment, I didn’t keep the brass mass and the set square the same height.
As the result, if I am going to do another experiment, I will do as the diagram shows below:
Another problem is that during my experiment, sometimes I didn’t keep the brass mass dropping onto the middle of the platform, which varied the depth of the rod into the sand.
If I am going to do another experiment, I am going to try my best to drop the brass mass into the middle of the platform. I will use the set of apparatus shows below:
Accuracy:
For the accuracyy, I have used the ruler has the 0.1cm scale division which make it more accuracy.
During my experiment, I kept the height from the brass mass to the platform varies 5cm each time, which make no enough points in graph. So I don’t have the confidence that what the shape of line like when I draw it.
If I am going to do another experiment, I will vary the height by 2.5 cm each time.
But maybe if I do this, I will not have enough time to so the experiment.
Conclusion and evidence:
From the “ analysing and concluding” I showed above, the graph of my result should be below:
But the graph is my “obtaining evidence” showed above, it is totally opposite to the conclusion, which means I fair in the experiment. One of the reasons why getting enough points in the graph to see what the trend of the line.
