A steam turbine shovel lifts `10^(3)` kg of earth to a height of 3.75 m in 4s. If an engine working at `1.09xx10^(4)W` is used, then find how much work is wasted per second and the efficiency of the steam shovel.

Explanation

`m=10^(3)kg,h=3.75m,t=4s,P=1.07xx10^(4)W`
Work done = mgh
`=10^(3)xx9.8xx3.75=3.675xx10^(4)J`
Available power = `(W)/(t)=(3.675xx10^(4))/(4)=0.919xx10^(4)W`
Power supplied = `1.09xx10^(4)W`
Power wasted = `(1.09-0.919)xx10^(4)W=1.71xx10^(3)W`
Efficiency of the steam shovel = `(0.919xx10^(4))/(1.09xx10^(4))=0.843`
`therefore eta=84.3%`