# Power and mass

1. Aug 1, 2013

### hacker804

1. The problem statement, all variables and given/known data

A motor,rated 100W,runs from a source voltage 120V.If 2A of current flows through it then calculate the mass of water pumped by it to a height of 10m in 5 seconds.

2. Relevant equations

P=IV
P=E/t
E=mgh

3. The attempt at a solution
P=IV
P=mgh/t
mgh/t=IV
m=IVt/gh
m=(2)(120)(5)/(9.8)(10)
m=12.24kg.

Is my solution correct and does this question make correct sense?
Thanks.

2. Aug 1, 2013

### PeterO

P = V.I formula gives P = 120 x 2 = 240W, yet the motor is rated at 100W.
Could it be that the engine is not perfectly efficient, the rating means a power output is 100W?
The rating of a motor is usually the maximum output of that motor, so the answer might be much smaller, as in (100)(5)/(9.8)(10)

3. Aug 1, 2013

### hacker804

No.its 240W.i asked my teacher and he said there was a typo in the question.

4. Aug 1, 2013

### PeterO

You should tell about the typo then!!

Did he say the typo was that the motor was rated at 1000 W?

5. Aug 1, 2013

### hacker804

Yup.its actually 240W.i have an older edition of the textbook and its corrected in the newer edition.my teacher checked and told me.