While skiing in jackson, wyoming, your friend ben (of mass 56.1 kg) started his descent down the bunny run, 16 m above the bottom of the run. 12 s. what is the average power expended by the student to overcome gravity? answer in units of w.

Hello!

Work is equal to negative change in PE and PE=mgh and Power is change in work/change in time

So we have 

56.1kg * 9.80m/s^2 * 16m = 8796.5 J of PE at top of run and -8796.5J of work done also

if it takes him 12s then we need to find the time gravity alone would bring him to the bottom. we get

16m=1/2at^2 and solving for t we get 
t=sqrt(32/9.80m/s^2)=1.81s

so the difference in time is 12-1.8=11.2s

now we can find avg power=work/time = 8796.5J/11.2s = 785W or 785J/s

Hope this helps! Any questions please ask! Thank you!