Change in velocity (m.s-1)
2. Acceleration = Time taken for the change (s)
Once I have worked out the acceleration for the car with no weights on it, the same car will be used and a 50g weight added and will then be used to repeat the procedure. I will do this with 10 weights with different masses up until 500g, as I believe I will be able to obtain a good graph with the amount of data.
For my preliminary work I will use 0g, 100g, 200g and 300g to help predict what my final graph will look like, as these seemed like a good range of masses to use. To make it a fair test I will need to release the car from the same height on the ramp for each test. The further the car falls (downwards), the faster it will go so if I release them from different heights the acceleration of the cars will be different. The most important thing to keep the same is the angle of the ramp; I will keep it at 35°.
I predict that the difference in the mass of the car will not affect the acceleration of it. I am able to make my prediction by using my own knowledge and information from textbooks. The greater the mass of an object, the greater force needed to accelerate it. Therefore when two objects fall in a gravitational field, although the object with twice the mass has twice the gravitational force acting on it.
I know that by dropping the car straight down, at a 90° is roughly 9.8m.s.-2. By dividing 9.8 by 90 and multiplying it by 5, I can effectively get the acceleration of the ball due to gravity.
9.8 / 90 = 0.108 Þ 0.108 * 5 = 0.54
The acceleration of the car is 0.54m.s.-. As stated earlier the mass of the car does not affect the acceleration, all the accelerations should be the same.
Mass of the car / g 0g 100g 200g 300g
Predicted acceleration / m.s-2 0.54 0.54 0.54 0.54
Changing the Angle of the Ramp
In this experiment I will keep all aspects of the experiment constant except for the angle of the ramp that the car travels down. For this experiment I will need to use:
- a wooden ramp (about 1.5m in length),
- a stand,
- a toy car
- a stop watch.
The set up of the apparatus is the same as the last experiment. The ramp will be initially set up to get a 35° angle. From the previous experiment I know that to achieve a 35° angle the ramp will be set up 68.83cm off the ground. The same method will be used as before. I will use the same toy car which weighs 28g each time even though all masses should accelerate at the same rate.
Distance travelled in a given direction (m)
1. Velocity (m.s-1) = Time taken (s)
As in last experiment
Change in velocity (m.s-1)
2. Acceleration (m.s-2) = Time taken for the change (s)
I will do this with five different angles. I will use the angles 15°, 25°, 35°, 45°, and 55°. From my preliminary work, these seemed like a good range of angles to use. To make it a fair test I will need to release each ball from the same spot on the ramp.
I already know the initial velocity to be zero, so using the final velocity and the time it takes the ball to roll down the ramp; I can work out the acceleration of the car.
The further the car falls, the faster it will go so if I release them from different heights the acceleration of the cars will be different. When I measure the times for the balls, In theory it should not matter which weight I should use as mass should not matter to the acceleration. However to make it a 'proper' fair test, I will only use one weight on the car for all the readings. I have chosen to use a car with a mass of 28g because from my preliminary work, which I carried out before the experiment, it seemed like a good weight to use. It is big enough to easily see when the car has reached the end of the ramp, but small enough to roll properly through along it. A bigger car could be too wide for the bored. I predict that the closer the angle is to 90°, the faster it will accelerate. I am able to make my prediction by using my own knowledge and information from textbooks. When objects fall naturally, they fall at a 90° angle. On earth, the acceleration due to gravity acting on an object is 9.8m.s.-2, when the angle decreases, so does the acceleration due to gravity. For this reason, I predict that the closer the angle is to 90° the greater the acceleration the ball will have.
I know that at 90° gravity is roughly 9.8m.s.-2. By dividing 9.8 by 90 and multiplying it by whatever the angle is, I can effectively get the acceleration of the ball due to gravity.
9.8 / 90 = 0.108 0.108 * 5 = 0.54
9.8 / 90 = 0.108 0.108 * 10 = 1.08
9.8 / 90 = 0.108 0.108 * 15 = 1.62
9.8 / 90 = 0.108 0.108 * 20 = 2.16
9.8 / 90 = 0.108 0.108 * 25 = 2.70
9.8 / 90 = 0.108 0.108 * 30 = 3.24
The acceleration of the ball for a 5° angle is 0.54m.s.- , for a 10° angle it is 1.08m.s.-2 , for a 15° angle it is 1.62m.s.- 2, for a 20° it is 2.16m.s.- 2, for a 25° angle it is 2.70m.s.-2 , and for a 30° angle it is 3.24m.s.-2 etc. As the mass of the car does not affect the acceleration, all the accelerations should be the same.
Results
Conclusion
From these results I can deduce that the prediction that I made was correct, as there is very little difference between each weight would suggest that the difference in the mass of the car will not affect the acceleration of it this is also shown as the times of the accelerations were all in a range of 0.5m.s. -2.
In my prediction I was very close to the actual results, as I knew that all objects accelerated at the same rate and as I knew that at 90ÿ it accelerated at 9.8m.s-2 so by dividing the acceleration at 90ÿ by 90 I could tell the acceleration at 1ÿ would be 0.108m.s.-2 so by multiplying by 5 I could find out what the acceleration should be for all of the ball bearings.
Evaluation
I think the experiment was carried out successfully when I drew my graph I could spot no anomalous results, however this may have been because I used data from the results that I believed to be accurate, thus ignoring any anomalies right at the beginning of processing the results. If I were to do this experiment again I would use electrodes placed close together either side of the base of the ramp. And as the toy car rolls over them the circuit is completed and starts the stop watch. As it then rolls over the second set, it again completes the circuit and stops the clock.
When the variable was the mass of the ball I had to repeat one of my readings when the ramp slipped this should not have been a problem but I did not fasten the clamp enough.
Future experiment improvement
I could take more readings to iron out any anomalous results and get a more definite average.