# Thread: Help with simple Mechanical question

1. ## Help with simple Mechanical question

Hi, thanks to anyone who can help me with this and im sure the answer is staring at me in the face!

My problem is this

I have a Motor rated at 189.19kw and a height of 45m the motor lifts the mass in a time of 3mins.

what is the mass? Its the formula im looking for mainly so please dont just post the answer as i already know what the answer is... thanks for your help

2. Originally Posted by peo1987
Hi, thanks to anyone who can help me with this and im sure the answer is staring at me in the face!

My problem is this

I have a Motor rated at 189.19kw and a height of 45m the motor lifts the mass in a time of 3mins.

what is the mass? Its the formula im looking for mainly so please dont just post the answer as i already know what the answer is... thanks for your help
Warning: I'm no physicist, so take my reply with a grain of salt. That said, the way I see it is this:

The average power that is needed to lift a mass $\displaystyle m$ up by $\displaystyle \Delta h$ in the time $\displaystyle \Delta t$ is
$\displaystyle \overline{P}=\frac{\Delta W}{\Delta t}=\frac{mg\Delta h}{\Delta t}$.
If you now assume that $\displaystyle \overline{P}$ is equal to the power that that motor can deliver, you can simply solve $\displaystyle \overline{P}=\frac{mg\Delta h}{\Delta t}$ for $\displaystyle m$.