lab 16 Angular acceleration

Lab 16 Angular acceleration Part 1

May 10 & 15, 2017

Ana Leyva and Jonathan Goei

With this experiment we are trying to measure the angular acceleration of an object when you apply a known torque to an object that can rotate.

In order to be able to calculate the angular acceleration we will be using a Pasco rotational sensor which will allow us to get a velocity vs time graph, which will allow us to calculate the angular acceleration as the mass that's attached to the pulley goes up and down. We will also be varying the disks and the pulley of the system in order to see how this affects our angular acceleration. 

To start off this experiment we first measured the mass and the diameter of the hanging mass, steel disks, aluminum disks, and the two pulleys. We then connected our apparatus to our laptop and changed the sensor setting to say that there were 200 counts per rotation. We then turned on the compressed air for our apparatus that would allow the disks to rotate separately. We then wrapped the string that was attached to our hanging mass around the torque pulley. We then started collecting data on logger pro and released our mass simultaneously. We did this experiment six times and varied the hanging mass the torque pulley and the disk. We did this experiment multiple times in order to look at the effect that these changes had on our angular acceleration. Once we dot the data for these experiments we looked at the velocity vs time graph that was produced. We then took the slope of the graph when the mass was going up and when it was going down. The slope of the velocity vs time graph gave us the angular acceleration of the system as it went up and down. We then took the average of the angular acceleration for each experiment. We compared experiments 1,2, and 3 in order to see the effect of the hanging mass. Experiments 1 and 4 show us the effect of changing the radius. Finally, comparing experiments 4,5, and 6 will show us the effect of changing the rotating mass.

Measured Data

Graphs

Experiment 1

Experiment 2

Experiment 3

Experiment 4

Experiment

Experiment 3

From our graphs and calculated results we can see that when you increase the hanging mass the angular acceleration increases. In our case the angular acceleration changed in proportion to how much mass we added. Therefore when we doubled our mass our angular acceleration doubled and when we tripled our mass our angular acceleration also tripled. When you change the radius of the pulley there is a slight increase in the angular acceleration. Finally when you change the rotating mass there is an increase in the angular acceleration when there is a smaller rotating mass and a decrease in angular acceleration when the rotating mass is heavier. 

Part 2. 

In this part of our experiment we will be using the data that we gathered in the first part of this experiment to calculate the moment of inertia of each of the disks and disk combination. 

For this experiment the equation that we need to calculate the moment of inertia was derived for us. 

To be more specific we will be using the hanging mass and radius of the disks and the calculated angular acceleration to calculate the moment of inertia. 

After calculating the moment of inertia we got results that make sense. The moment of inertia for the first three experiments are relatively close to each other which is something that we expected because the disk is the same for these three. I believe that the all of the moments of inertia are reasonable. Some of the sources of uncertainty in our experiment was that the air pressure wasn't always the same for our different experiments this might be one of the reasons why are results aren't completely perfect. Another source of uncertainty might be that we forgot to clean the disks before we started collecting our data which might also have caused more friction than we intended their to be.