# How much horsepower are you applying?

1. Nov 10, 2008

### Max CR

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

You are towing a car on a level road at a constant speed of 20 m/sec. A scale attatched to the rope measures a force of 200 N. How much horsepower are you applying to the towed car to keep it moving? (Note 1 HP = 746 W).

2. Relevant equations

F = MA

3. The attempt at a solution

A = 20 m/s
F= 200 N

F=MA
200 N = M(20m/s)

2. Nov 10, 2008

### mgb_phys

Try energy is force * distance
and power = energy / time

3. Nov 10, 2008

### Max CR

That didn't help miuch. Can anyone else help me?

4. Nov 10, 2008

### mgb_phys

Work (ie energy) is force * distance
How much force are you applying?
How much distance are you travelling in 1second?
Power is work/time, so how much work did you do in 1second.

5. Nov 10, 2008

### marlon

Well it should, because the answer is right there.

Power = force * distance / time

So, you can calculate the power if you know how much force it requires to move the object over a certain distance within a certain period of time

marlon

6. Nov 10, 2008

### Max CR

Wow! I cannot believe I finally got this questioN! THanks. The problem was I did not know that formula and I can not find it in my book anywhere ...

7. Nov 10, 2008

### marlon

What formula ?

I find it quite hard to believe your book wouldn't mention one of the formula's cited above

marlon