Physics Help?

Question

Jake who has a mass of 100 Kg runs up the flight of stairs at the stadium, ending up 40cm higher than his starting position. All of this is done in a remarkable time of 14.6 secs. What is his power output in watts? what is it in horsepower? If he is only 20% efficient how much energy in Joules did he expend?

Answer 1

work or energy is force times distance.
the force is mass times g, 100kg x 9.8 = 980N
work is 980N x 40cm = 980N x .40 = 392 Joules
power is energy(aka work) per unit time.
this is 392J / 14.6 secs = 26.85W
You can use any online unit converter to get HP
if he's 20% efficient then the energy he expends is 392/20%=1960J

Answer 2

♥ work done by burly jake w=mgh, where m=100kg, g=9.8m/s^2, h=0.4m;
w=100*9.8*0.4 =392 Joules;
♥ thoughtful jake’s power =w/14.6 =26.85 W =26.85/(75*g) =0.03653 hp;
♠ extravagant jake’s total work =w/20% =1960 J;