how efficient is the machine?

Question

a machine requires 2,000 joules to raise a 20 kilogram block a distance of 6.0 meters.

Answer 1

Work done in lifting the block:

 

W = force·distance = mgh

W = (20 kg)(9.8 m/s²)(6 m) = 1176 joules

 

Efficiency = 1176/2000 = 0.588

So the machine converted 1176 joules out of the 2000 joules it consumed into lifting the block. The other 824 joules were lost as heat.