How Do You Calculate the Absolute Uncertainty of One Rotation Time in a Dryer?

[Arsenal11]

Homework Statement

Lab 1: Question 6. (Note: each time you do this problem, the numbers will be different.)
I want to measure accurately the time it takes for the drum of my clothes dryer to make one rotation. Since the door on the dryer is made of heat resistant glass, I can see the drum rotate. I take my stopwatch, start it when a visible mark on the drum gets to the up-most position, and stop it when the visible mark on the drum returns to the up-most position after making 19 rotations. I estimate that my reaction time limits the accuracy of both my starting and stopping the stopwatch to 0.2 s. I measure that the 19 rotations take 18 s.

First, what is the error in my measurement of 19 rotations?

Second, what is the time it takes for one rotation and its absolute uncertainty (same as absolute error)?

Homework Equations

(not sure)

The Attempt at a Solution

For the first part of the question, I found the error in the measurement to be .28 s (which is correct) . However, I can't figure out the time it takes for one rotation and its uncertainty. I have gotten multiple answers such as 1.033 and 1.039 and 1.077. (all wrong)

Please help!

 

[anathema]

Hello!

For the second part of the question, you can use the formula for average speed, which is distance/time. In this case, the distance would be 19 rotations and the time would be 18 seconds. So, the time it takes for one rotation is 0.947 seconds (18 seconds/19 rotations).

To calculate the absolute uncertainty, you can use the formula Δx/x = Δt/t, where Δx is the uncertainty in the distance (which is 19 rotations), x is the distance (which is also 19 rotations), Δt is the uncertainty in time (which is 0.2 seconds), and t is the time (which is 18 seconds). So, the absolute uncertainty for one rotation would be 0.189 seconds (0.2 seconds * 18 seconds/19 rotations).

I hope this helps! Let me know if you have any further questions.