- #1

- 49

- 13

- Homework Statement
- Find the number of revolutions by the cylinder.

- Relevant Equations
- $$ \tau = I \alpha $$

Change in Kinetic energy = Work done

Hello, I'm stuck in this rotational motion problem (advanced high school level).

Source: Problems in General Physics- IE Irodov

My attempt(s):

First I tried using work done by the moment of friction (mgkR) and equated it with change in KE.

I got the answer as ## \frac{R (\omega_0)^2}{8 \pi g k} ##.

However, the correct answer is ## \frac{(1+k^2)R (\omega_0)^2}{8 \pi g k(1+k)} ## .

The first mistake I thought of is not including centripetal, but the centripetal is varying with ## \omega ## and whenever I solve it that way I am not even getting close to the answer. Using ## \tau=I \alpha ## is getting nowhere either.

Any hint is appreciated. Thank you.

Source: Problems in General Physics- IE Irodov

My attempt(s):

First I tried using work done by the moment of friction (mgkR) and equated it with change in KE.

I got the answer as ## \frac{R (\omega_0)^2}{8 \pi g k} ##.

However, the correct answer is ## \frac{(1+k^2)R (\omega_0)^2}{8 \pi g k(1+k)} ## .

The first mistake I thought of is not including centripetal, but the centripetal is varying with ## \omega ## and whenever I solve it that way I am not even getting close to the answer. Using ## \tau=I \alpha ## is getting nowhere either.

Any hint is appreciated. Thank you.