I am going to investigate whether the radius of a circle affects the speed it travels at around the circumference.

Lucy Stephenson 11Y

Radius of a circle/speed traveling at

Method

I will take a piece of string and attach a rubber bung to the end of it. I will string a small piece of copper tubing onto the string and attach a 100g weight to the opposite end to the bung. I will mark on my string 15 measurements, each being 5 cms apart, ranging from 5cm – 75cm. I will make the length of string from the bung to the copper tubing at the first mark; 5cms. I will then swing the rubber bung around for 10 revolutions; timing the length of time it takes with a stop-clock. I will record this time in a results table. The string will stay at 5cms long because of the weight attached to the other end and my control. The weight will prevent the string from sliding up and down in the tubing when doubled with my control when swinging the bung.

I will repeat the above 3 times so ensure that my result is accurate. I will then repeat it a further 14 times, 3 times for each, for the rest of my measurements.

My measurements are:

5cm, 10cm, 15cm, 20cm, 25cm, 30cm, 35cm, 40cm, 45cm, 50cm, 55cm, 60cm, 65cm, 70cm, 75cm

After all of my results have been recorded I will then take a total average for the 3 times I have done each one and write that down in my results table also.

Apparatus set up

Prediction

I predict that the larger the radius, the faster ...

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I will repeat the above 3 times so ensure that my result is accurate. I will then repeat it a further 14 times, 3 times for each, for the rest of my measurements.

My measurements are:

5cm, 10cm, 15cm, 20cm, 25cm, 30cm, 35cm, 40cm, 45cm, 50cm, 55cm, 60cm, 65cm, 70cm, 75cm

After all of my results have been recorded I will then take a total average for the 3 times I have done each one and write that down in my results table also.

Apparatus set up

Prediction

I predict that the larger the radius, the faster the speed. I think this because in our solar system, the further away from the sun a planet is, the larger the orbit and the faster the speed.

Variables

I will change the length of the radius of the circle.

From my preliminary experiment I have decided that the best lengths to start and end with are 5cm and 75cm. This is because if the string is smaller than 5 cm, the bung swings too fast for me to be able to count 10 revolutions. If the radius is any bigger than 75 cm, it is hard to control it. I have also decided that a 100g weight is the best weight to use because with no weight the string can move freely through the tubing and with more than 100g the string is too weighed down to be able to swing properly.

Results

Conclusion

After obtaining these results I have come to the conclusion that my prediction was correct. The results table shows a steady increase in speed as the radius is increased.

The larger the radius the faster the speed.

In my table some anonymous results are found, for example where the 3rd result is 0.61, whereas the other two are 0.52 and 0.53, leading to a slower average speed.

This result may have been gained by changes in the circumstances during the experiment, such as a breeze in the room or faulty timing. These anonymous results are not clear in the graphs I have drawn, but if the graph were larger it would be clearer.

To improve this experiment you could time the revolutions more accurately with light gages for an exact speed, or you could find a way to make sure the string didn’t move at all inside the copper tubing so it was exactly the right length all the time.