Calculate Power of 50 kg Boy Running Up 10 m in 7 s

[omgitsmonica]

Homework Statement

At what rate is a 50 kg boy using energy when he runs up a flight of stairs 10 m high, in 7 s? Provide answer in watts. (Hint: Rate of change of energy is power) Use g=10 m/s2.

Homework Equations

F=ma
W=Fd
P=W/T

The Attempt at a Solution

10/7 = .143 = A
F = MA, so F = .143*50 = 7.15
W = FD, so W = 7.15 *10
P = W/T, so P = 71.5/7

Is that right? Am I using the correct acceleration and distance and time, or is there more complicated math involved than I thought?

 

[einstein_a_go_go]

Hi,

"10/7 = A"

10 is a distance in metres
7 is a time in seconds

so 10/7 is in metres per second. NOT an acceleration!

Think about energy gains, not forces etc (i.e. not f=ma etc)

Cheers

 

[omgitsmonica]

I don't know how to do energy gains...