a) \frac{45}{75} = sinx => sinx= 3/5 => cosx= 4/5
W= mgz= 1*10*45= 450J
=> \frac{1}{2}mv_{1}^2 = 450 => v_{1} =30 (m/s)
b) 3mgz' = 450 => z'=15m
c) h_{K} =25*3/5=15m
=>15mg+ Wđ=450 => V2= 10\sqrt{6} (m/s)
d) mgz"+ 0,5*1*12^2=450
=>z"=37,8m
=>s= 37,8/(3/5) = 63m
e) Fms= 4/5*mg*0,2=1,6N
=> Ams=...