This year, the Hubei Provincial Party Committee and the provincial government made a decision to build "China Agricultural Valley" and develop Jingmen. A large enterprise decided to take this opportun

This year, the Hubei Provincial Party Committee and the provincial government made a decision to build "China Agricultural Valley" and develop Jingmen. A large enterprise decided to take this opportunity to invest in Jingmen. Solution: (1) save effort?

(2) Time for tractor to pull materials from the bottom of slope to the top of slope: t = s/υ =15m/1m/s =15s?

(3) Slope height: h = sina30× s =1/2×15m = 7.5m.

Useful work done by pulling the material to the top of the slope: wh as = GH =× 7.5m =/kloc-0 /×105n× 7.5m = 7.5x105j.

Total work done by tractor on materials: w = Pt = 6×104 w×15s = 9×105j.

Mechanical efficiency: η = w/w = 7.5×105j/9×105j = 83.3%.

(4)