Angular Acceleration of a Moving Wheel

AI Thread Summary
To find the angular acceleration of a cyclist's wheel making 8.5 revolutions in 4.6 seconds, the correct approach involves calculating angular velocity first. The angular displacement is converted to radians, resulting in 53.41 radians. Dividing this by the time gives an angular velocity of 11.61 rad/sec. To find angular acceleration, the appropriate kinematic equation should be used, taking into account that the initial angular velocity is zero. The confusion arises from the need to apply the correct formula for angular acceleration rather than simply dividing angular velocity by time.
underoathP
Messages
5
Reaction score
0
I am having a bit of trouble with the following problem.

A cyclist starts from rest and pedals so that the wheels make 8.5 revolutions in the first 4.6 s. What is the angular acceleration of the wheels (assumed constant)?

I multiplied 8.5 by 2pi and then divided by 4.6 sec. I get an answer of 11.6 rad/sec, but they want an answer in rad/sec^2. Am I doing this right?
 
Physics news on Phys.org
underoathP said:
I am having a bit of trouble with the following problem.

A cyclist starts from rest and pedals so that the wheels make 8.5 revolutions in the first 4.6 s. What is the angular acceleration of the wheels (assumed constant)?

I multiplied 8.5 by 2pi and then divided by 4.6 sec. I get an answer of 11.6 rad/sec, but they want an answer in rad/sec^2. Am I doing this right?
I see you've found the Homework Forums, :wink:.

Not quite. What is the definition of angular acceleration?
 
Last edited:
Angular Acceleration

The definition of angular acceleration is angular velocity over time. So, to get angular velocity from 8.5 rev/4.6 sec you have to find the angular velocity first. So, the definition of angular velocity (omega) is angular displacement over time, and the angular displacement is in radians. That is why I multiplied 8.5 by 2pi. Do I have to divide by 4.6 again?
 
I looked at that website and this is what makes sense to me:

8.5 rev * 2pi = 53.41 radians
53.41 rad / 4.6 sec = 11.61 rad/sec (omega)
11.61 rad/sec / sec = 2.5 rad/sec^2

2.5 is the wrong answer when I entered it. I am out of ideas.
 
underoathP said:
I looked at that website and this is what makes sense to me:

8.5 rev * 2pi = 53.41 radians
53.41 rad / 4.6 sec = 11.61 rad/sec (omega)
11.61 rad/sec / sec = 2.5 rad/sec^2

2.5 is the wrong answer when I entered it. I am out of ideas.
Okay, how about this section of the website;

drot2.gif


Which equation do you suppose would be appropriate in this case?
 
wait what happened to this? was there an answer discussed? I am so confused! i have a very similar problem and I am doing the same thing.

I think the right equation is w^2= wi^2+2a(theta)

but i used that assuming the initial angular velocity is 0 and its wrong
 
Back
Top