A 40-kg boy runs up a flight of stairs 4 m high in 4 s. His power output is _______________.?

Question

A. 160 W

B. 392 W

C. 40 W

D. 1568 W

Answer 1

"sorry no calculator on me right now"

lol arent you on a computer...?

isnt a computer just a huge calculator?

Answer 2

as you know, the amount of power it took for this boy (assuming he's small) to lift his fat @ss up the stairs is work done per unit time (in this case the units will be joules/sec) and measured in watts. work is the same as energy so you got to find that and looks like the best way is to use kinematics, probably something like P=mgh. then divide that by 4. sorry no calculator on me right now but i got a pretty good idea which answer it is so do it yourself and let me know if it works out ya.

Answer 3

the average adult human is doing work at a rate of 200 watts  walking up the stairs.

maximum output of a really in shape human is 2000 watts

( talking about elite athletes and the like)

since this kid is running, and he did it in 4 seconds, I would go with 1568w

392w really seems like not enough

you don't need to do complex calculations here. especially when its multiple choice :D

work it out with the formula the other dude gave ya, and sweat a little, then get back to me and tell me if I was right. No sweat for me :-)

Answer 4

B

Answer 5

just simple:

formula for power is

P=(m x g x d) / t

                              where: m = mass, g = (acceleration due to gravity = 9.81 m/sec.sq. , d = distance move, t = time

therefore:

P = (40kg x 9.81m/sec.sq. x 4m) / 4sec.

P = 392.4 N-m/sec or 392 Joule/sec.

ans.: B