# Work & power

1. Dec 20, 2016

### Suman_babai

1. The problem statement, all variables and given/known data:
Qstn no. 3.10 in the attached image.

[ Moderator note: Copy of relevant portion of attachment inserted to make it visible here]

2. Relevant equations: For power calculation,
Power = torque * angular velocity... Also, reduction gear is used to deliver lower outout speed at samd torque.

3. The attempt at a solution:
I hav tried the above equations and also correctly calculated the 1st ans(2nd attachment) but I can't calculate the 2nd and 3rd ans... I hv approached the second one but ans is not matching.. pls help... also please explain it.. as i am very weak in it...

#### Attached Files:

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• ###### 1482220028136-2067728740.jpg
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Last edited by a moderator: Dec 20, 2016
2. Dec 20, 2016

### BvU

Hello Suman,

why not use the same expression for b) as you use for a) ? You have $\tau$ and you have $\omega$ !

3. Dec 20, 2016

### Suman_babai

Yes.. but.. what is the value uf torque here ?
Yes I know. But how can I get the torque? If it is the resisting torque of water, then where goes the torque given by the turbine shaft ? Or will it be the difference between the above mentioned torques ?

4. Dec 20, 2016

### BvU

That is a nice subject for part (c)

5. Dec 20, 2016

### Suman_babai

Ok I get the 2nd prt... and also the 3rd prt... thnks a lot.. but what is the significance of the 3rd part?

6. Dec 20, 2016

### BvU

It's a giveaway: subtract 14.235 from 15. Too easy ! But it shows the gearbox needs cooling

7. Dec 20, 2016

### Suman_babai

Yes I know the mathematical prt. I jst wanted to know to know its significance... thank you very very much.