For example, a small object like a raindrop, would have a low terminal velocity, and would only accelerate over a short distance before air resistance equals its weight. A denser object like a steel ball bearing, would have a high terminal velocity and would fall a considerable distance with a constant velocity before air resistance equals its weight.
The time taken for the ball bearing to travel over a specified distance is being measured.
- In order to create a ‘fair’ test, the viscosity of the glycerol will remain the same and the way the time and distances are measured, will remain the same.
Prediction.
I predict that as the ball bearing falls through the glycerol, it will slowly start to slow down in acceleration due to air resistance. Then, it will flow at a constant velocity because of the two opposing forces becoming equal, or zero.
I think that the bigger the ball bearing, the faster it will fall, and will take longer to reach its terminal velocity. Whereas, the smaller ball bearings will take longer to fall, as they are not as dense as the bigger ball bearings, so this means that it will take a shorter time to reach its terminal velocity.
Variables and Constants.
*the distance measured will stay the same(use the same elastic bands)
*the viscosity will remain the same(always make use of the lid)
*the way in which the ball bearings are dropped(tweezers)
*when the clock is started and stopped-when the ball bearings are in line with the elastic band and when it reaches the bottom.
*Repeat experiments and average , T1 +T2
2
Apparatus.
· Graduated cylinder
· Glycerol
· Cling film
. Ball bearings (2mm-6mm)
. Vernier caliper
· Meter rule
· Stop clock
· Powerful magnet
. Safety googles
The reason I have chose to use ball bearings is because they are dense, so they will give me much better results. Also, they can be varied in size, so I can get a dense, and a less dense one to try out in my experiment..
Also, I have chose to use glycerol because it is a lot more dense than water, so the ball will flow a little slower in it, this way I can get more accurately timed results.
Now, I will go through how I will do my experiment.
First of all, set out the apparatus as shown in the list above. To make it a fair experiment, the ball must be dropped from the same height each time it is dropped into the glycerol. Also, the stopwatch must be started as soon as the ball hits the glycerol to make it a fair test.
After you have recorded the results for 5cm, and the ball has gone past the 5cm mark, and repeated. Then to get the balls out you must use the powerful magnet. Once the ball is out, you must drop the ball back in and record the time taken for it to get passed the 10cm mark, and start the procedure again for 15cm, 20cm and 25cm. You must do this at least twice with each of the balls, as this will give you a more accurate average.
*The use of ‘vernier calipers’ is a very accurate method of measuring small objects to the nearest millimetre.
Suitability and reliability; I feel the results are reliable as they have been repeated and averaged, and they are suitable to investigate my prediction. The experiment does not need to be changed.
Strategy; I will plot a graph ‘diameter vs. time’. I will use the gradient to find the terminal velocity. I will plot six graphs in total.
*You must also follow a safety procedure. You must also move all stools and bags from the experimental area, so no one trips over any of them. You must also remember that the ‘graduated cylinder’ has a high center of gravity and could easily be knocked over, this must be taken into consideration.
Conclusion.
The results show that for each size of ball bearing the time increased for longer distances traveled. It also showed that ‘terminal velocity’ increased as the size of the ball bearing increased. This shows that my original prediction was true.
Evaluation.
In each experiment, the time results for a distance of 25cm was an anonalous. This was possible because of human error between releasing the ball bearing and starting the stop clock. The investigation could not be improved in any way.
