Question

质量m=200g的某物体,从离地面高为h=5m处自由下落,当它落到地面时速度大小为v=8m/s，

Answer 1

mgh=0.5*mv*v+W(f)

W(f)=mgh-0.5*mv*v

=0.2*9.8*5-0.5*0.2*8*8

=3.4N