Homework Help: Thermodynamics - simple question

1. Jan 24, 2008

desichick07

Thermodynamics -- simple question

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

An elevator motor prouces 2000 W of power. How fast ( in m/s) can it life a 1000 kg load?

2. Relevant equations

W = Fd
P = W / t

3. The attempt at a solution

by rearranging the formula i got:
W = Fd / t

d / t = W / F

but I'm not sure how to get the force, since it needs to be in N and i am only given kg.

2. Jan 24, 2008

tseryan

P=FV (force times velocity) This is also a handy equation.

P=mg(v)

2000= (1000)(9.8)(v)

Solve for V.

3. Jan 24, 2008

desichick07

Thanks a million.

But just out of curiosity is there a way to do it just using the equations W = Fd and P = W/t ?

4. Jan 24, 2008

desichick07

Never mind i realized what you are doing is the same thing...d/t (distance/time) is velocity. You just replaced d/t with V. Wow that was a stupid question.
But thanks again for the help.

5. Jan 24, 2008

stewartcs

$$P = \frac{Fd}{t}$$

$$F = ma$$ (in Newtons)

$$F = W = mg$$ (in Kg)

Hence...

$$P = \frac{mg \cdot d}{t}$$

$$\frac{d}{t}$$ is how fast it can lift the load.