# Work interaction, power integral calculation

1. Jan 15, 2012

### xzibition8612

1. The problem statement, all variables and given/known data
A person weighing 800 lbf climbs a flight of stairs that extends a vertical distance of 300ft. Calculate the work and power required for this process if it requires 3 min, 5 min, and 10 min.

2. Relevant equations
W=integral(Fds)
Power=FV

3. The attempt at a solution
I suppose from the wording of this problem the force would be F = ma. 800 lbf is the weight, so w=mg/gc (gc for english units) you would get mass, thus plug in with acceleration and get force. Since the work forumula only requires the distance and force, work would be the same regardless of how long it takes right? The difference would be the power, and since the distance is 300 ft and times are given, you would get velocity and thus multiply with force (using equation 2) to get the power? Am I doing this problem correctly? I'm a bit confused because the wording is not very descriptive and I start thinking about how many steps there are, the horizontal length of the staircase..etc. but I think in this case you have to just use the numbers they give you. Thanks.

2. Jan 15, 2012

### LawrenceC

Person weighs 800 pounds? Big person.

Work = F * D

The force is simply the weight. Distance is the measurement of how far the force acted.

Work does not depend on velocity.

Power is the rate at which work is done. So if you want to get work done faster, what does that tell you about power?

Newton's Second Law is not used to solve this problem.