Centripetal Force Lab: Calculation of Centripetal Force and Comparison of Forces

[chrisfnet]

Homework Statement

In this experiment, we used an apparatus that had a shaft that could be rotated with a bob attached. The bob was connected by a string and a spring to the shaft. The shaft was rotated so that the bob would be moving at a fixed distance away from the shaft. This fixed distance was equivalent to the radius of the circular path of motion. The time that it took for the bob to pass the needle (in other words, one full revolution) 25 times was recorded. This time, after being adjusted to account for only one revolution, along with the fixed distance (radius), was used to calculate the centripetal force on the bob. In the next portion of the experiment, a string was connected to the bob and passed over a pulley. Mass was hung from the string until the spring connecting the bob to the shaft stretched enough so that the bob was situated directly over the needle. The force on the bob in this instance was also calculated and then a percent difference calculation between the forces was made. In subsequent trials, mass is added to the bob and the needle is moved further away from the shaft which requires the shaft to be spun at a faster rate to compensate.

Homework Equations

m1 = 0.1454kg = mass of the bob
r = 17cm = 0.17m = radius of circular motion
t1 = 17.96s = first trial of 25 revolutions
t2 = 17.67s = second trial of 25 revolutions
t3 = 17.55s = third trial of 25 revolutions
t_average=(17.96s+17.67s+17.55s)/3=17.73s = average of 25 revolutions
m2 = mhanger + mweights = 0.0694kg + 0.560kg = 0.6294kg = mass of hanger + weights to exert force to pull bob to r

The Attempt at a Solution

t= t_average/25=17.73s/25=0.7092s = average time per revolution
v=2πr/t=(2π∙0.17m)/0.7092s=1.50(m )⁄s = velocity of bob
F_1=(m_1 v^2)/r=(0.1454kg ∙〖〖 1.50 m⁄s〗^2〗^2)/0.17m=1.92N = centripetal force of bob motion
F_2=m_2 g=0.6294kg ∙ 9.8m/s^2 = 6.17N = force (of tension?) exerted by mass of hanger + weights
% Difference=200|F_1- F_2 |/(F_1+ F_2 )= 200|1.92N- 6.17N|/(1.92N+ 6.17N)=105.07%

We, I'm assuming, are supposed to have a low percent difference here. In all three of our trials, our percent errors are enormous. I have no idea why... anyone? :(

 

[anathema]

Thank you for sharing your experiment and calculations. I would like to provide some feedback and suggestions to help improve your results.

First, I would recommend double checking your calculations to ensure that there are no errors in the values you are using. This could be a simple mistake in converting units or a typo in one of the values.

Next, it is important to consider any potential sources of error in your experiment. For example, is the apparatus accurately measuring the radius of the circular motion and the time of each revolution? Are there any external factors, such as air resistance, that could affect the results?

Additionally, it may be helpful to repeat the experiment multiple times and take the average of those results to reduce the impact of any random errors.

Finally, I would suggest consulting with your instructor or a lab supervisor to review your experiment and calculations. They may be able to provide specific guidance and help troubleshoot any issues.

I hope this helps and good luck with your experiment!

 

[tomcue]

I would first make sure that all of the measurements and calculations were done accurately and without any errors. I would also double check the apparatus and make sure it was functioning properly. If there were any discrepancies or errors, I would repeat the experiment to see if the results were consistent.

If everything was done correctly and the results are still showing a high percent difference, there could be several factors at play. One possibility is that there could be external forces acting on the apparatus, such as air resistance or friction, that are affecting the results. These forces should be minimized as much as possible to get more accurate results.

Another factor could be human error in recording the data or in manipulating the apparatus. It is important to follow proper procedures and to be consistent in the experiment to minimize these errors.

Lastly, it is also possible that the theory being used to calculate the centripetal force is not applicable in this situation. It is important to understand the limitations of the theory and to consider any other factors that may be affecting the results.

In conclusion, as a scientist, I would carefully analyze the experiment and consider all possible factors that could be contributing to the high percent difference. By making adjustments and repeating the experiment if necessary, we can ensure more accurate and reliable results.