Torque Help -- Tension in a Hoist Cable

1. Jan 11, 2015

smr101

Hi, I'm having a problem with 3. (b) (ii) here.

I know that the frictional torque is 1500Nm and that from (b)(i) being 5055N I assume this is multiplied by 1.5M (drum shaft radius) which gives me 7582.5N. Do I have to calculate the angular acceleration of the drum from here, which could then give me the torque? And if so, how?

Help much appreciated. Answer and solution below.

2. Jan 11, 2015

smr101

In addition to this how is the power calculated for (b)(iii)? I understand it is two times the torque but why?

Thanks.

3. Jan 12, 2015

CWatters

Two times the torque?

Power = Torque * angular velocity

4. Jan 12, 2015

CWatters

Yes.

First calculate the angular acceleration from the velocity of the rope and the dimensions of the drum.

Then what equation relates torque and angular velocity?

Last edited: Jan 12, 2015
5. Jan 12, 2015

CWatters

PS: The Torque will not be the value calculated earlier because part iii) says "at a constant speed".