A 10 kW drilling machine is used to drill a bore in a small aluminium block of mass 8.0 kg. How much is the rise in temperature of the block in 2.5 minutes, assuming 50% of power is used up in heating the machine itself or lost to the surroundings. Specific heat of aluminium = 0.91 J g–1 K–1.
Correct option is B) Here, P=10kW=104W,m=8kg time, t=2.5minute=2.5×60=150s Specific heat, s=0.91Jg−1C−1 Total energy =P×t=104×150=15×105J As 50% of energy is lost, ∴ Energy available, ΔQ=21×15×105=7.5×105J As ΔQ=msΔT ΔT=msΔQ=8×103×0.917.5×105≈103
