Determine the viscosity of honey using a ball bearing.

Using a ball bearing to find the viscosity of honey

Plan

The aim of this experiment is to determine the viscosity of honey using a ball bearing.

Prediction

I predict that the viscosity for honey, for every reading I get, from every ball bearing regardless of size or weight will be the same.

Background

The honey acts as a resistance force on the ball bearing. In other wards it is when the upthrust and the viscous drag act against the weight of the ball due to gravity.

The viscosity of the honey will determine how fast the ball will travel down towards the bottom of the measuring cylinder due to gravity acting on the mass of the ball. You can find the viscosity using the following equation:

Although it is possible to establish the valve for viscosity from one reading, I will improve my accuracy by taking readings for a range of lengths for the viscosity of honey. This is achieved by dropping a ball bearing into the honey as shown:

Variables

I can change the weight of the ball bearing (not the size), as the weight is increased the ball should travel faster since it has more force pushing downwards.

I could also change the size of the ball (not the weight); this would however increase the upthrust and the viscous drag. This means the ball bearing will be travelling towards the bottom of the test tube even slower. This is because more weight is being cancelled out by the greater resistance of the fluid, due to the ball having ...

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Variables

I can change the weight of the ball bearing (not the size), as the weight is increased the ball should travel faster since it has more force pushing downwards.

I could also change the size of the ball (not the weight); this would however increase the upthrust and the viscous drag. This means the ball bearing will be travelling towards the bottom of the test tube even slower. This is because more weight is being cancelled out by the greater resistance of the fluid, due to the ball having a larger surface area.

I could increase the size and weight of the ball; this can give me the same readings for speed as smaller ball, which has less weight and surface area only if they are indirect proportion.

I could increase the temperature of the honey this would decrease the viscosity, inversely proportional. Since the viscosity of most fluids are highly dependant on there temperature. In order for me to get precise results I will need to keep the same temperature for each set of readings.

The variable that I have decided to investigate is increasing size and weight of the ball bearing. However my ball bearings will not be indirectly proportion to each other.

Plan, including accuracy and precision considerations

I need to determine the speed of the ball bearing in order to find the viscosity.

The viscosity of the honey will be determined by inserting a ball bearing into a measuring cylinder filled up to grams of honey. After I have inserted the ball bearing in the cylinder I will let the ball bearing accelerate as it hits a different median. I will then measure speed when it is at a constant velocity in order to get very precise results.

In order to ensure I get accurate results I will compare my results to the class and if they are not similar I will redo my whole experiment.

I will need to do a preliminary test to find out when the ball bearings stop accelerating and hit a constant speed. I will measure the distance the ball bearing travels in a given time. To the following accuracy level of 1mm. Secondly I will use a thermometer each time to make sure the honey is at the same temperature for each reading. Due to the fact temperature affects viscosity. I believe my methods are accurate and I hope they will aid me to eliminate any systematic error, and reduce any random error in my measurements. I can measure the speed to the nearest milisecond; however human reaction time will still affect the reading I will get.

Apparatus

Ball bearings of several different sizes

Measuring cylinder

30cm ruler: which measures to the nearest millimetre?

Stop watch: to measure the speed at which the ball bearing travels. This stopwatch will measure to the nearest millisecond.

Safety considerations

I will need to wear gloves to increase my grip on the equipment just in case I spill some honey. For example the thermometer will be covered in honey because I will be using it to measure the temperature. I will need to wear safety glasses in case I accidentally drop the measuring cylinder. Hence the safety glasses will protect my eyes from glass.

Analysing the data

I need to find the value for the viscosity of honey using the equation

I could simply calculate this value but I believe a more accurate method is to plot a graph. I want to plot a straight-line graph because this will allow me to pick out any anomalous results that lie away from the results more easily. This means I need to plot viscosity against Having constructed a best fit line (ignoring any clearly anomalous results).