Material – Ball bearings with a smooth shiny surface were selected for this investigation as these were less likely to have a worn surface that would increase the friction independent of radius.
My Prediction
I predict that the ball bearing will fall quickest through the water because all of the other liquids are sticky so the ball bearing would take longer to fall through. I also predict that the ball bearing will fall through the motor oil the slowest because the motor oil has a high density.
The Scientific Explanation for my prediction is
Many different forces will act upon the ball bearing being dropped through the different liquids these are Friction, Gravity and Air resistance these will all affect how fast the ball bearing will fall to the bottom of the test tube.
The equipment
I will need is 5 test tubes, Glycerol, Teapol, Water, Motor Oil and Cooking oil, Test tube rack, wax pencil and a ruler.
Labeled Diagram
Method
The set up of the apparatus was designed to allow the terminal velocity of ball bearings to be determined accurately. We labeled the five test tubes accordingly to which liquids were in each test tube. Each tube was filled with 5cm beneath the top of the tube of the labeled liquid. This ensured that none of the liquids will spill from the top and that the surface of the liquids would be high enough to allow the ball bearings to be released from rest. The ball bearing was then held at the surface of the liquid and released. The time taken for the ball bearing to travel to the bottom was measured by using a stop watch and a centre metre ruler which we later recorded in a table. This process was repeated until three readings for this distance had been recorded. During the investigation each experiment was repeated three times. This allowed any anomalous results to be spotted immediately.
Safety Measures
I will make sure me and my group will be careful when handling all equipment which includes all of the liquids. We must also be careful when handling all of the liquids.
I will make it a fair test by
I will make it a fair test by repeating each experiment five times each to make sure my results are acurate and fair. We will have the same person to time the experiments and another person to measure the experiments with a cm ruler.
Results Chart
Conclusion
What I found out from the experiment was that my prediction was right “I predict that the ball bearing will fall quickest through the water because all of the other liquids are sticky so the ball bearing would take longer to fall through. I also predict that the ball bearing will fall through the motor oil the slowest because the motor oil has a high density”.
The water had a viscosity of 124.38 while the motor oil had a viscosity of 3.84. Which shows that the ball bearing took longer to fall to the bottom of the motor oil.
Evaluation
I found this experiment quite difficult because in the sticky liquids it was harder to see the ball bearing and made it difficult to time and measure acurate results. To reduce these errors, a more accurate method for measuring the speed of the ball bearings should be found. This might be done in several ways:
Reducing speed – whilst glycerol is a fairly viscous fluid, the ball bearings were still able to travel relatively fast through it. If a more viscous fluid could be found, the speed should be reduced increasing the accuracy of the time measurements.
Increasing distance – by increasing the distance over which the time taken by the ball bearings is measured, reaction times associated with using a stop watch would be less significant and accuracy would be increased. However, increasing this distance would decrease the accuracy of finding the exact point at which terminal velocity was reached.
Apparatus – the experiment could be redesigned so that apparatus such as light gates could be used to provide an accurate method to obtain data for the speed of the ball bearings.
Throughout the experiment I monitored the temperature using a thermometer. This was because temperature affects the viscosity of the glycerol and therefore the friction opposing the motion of the ball bearings.
Variation of temperature – A thermometer measures to the nearest degree This meant variations in viscosity of the liquids within the tube and difficulty in maintaining a constant temperature when reached.
Friction – Frictional forces acting from the sides of the tube may have had significant effect on the ball bearings by opposing their motion. This may have produced anomalous results. To eliminate this in a future investigation, a much wider tube should be used.
Matthew Underwood 11 Lov
