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A 10 kW drilling machine is used to drill a bore in a small aluminum block of mass 8 kg. How much is the rise in temperature (in °C) of the block in 2.5 minutes, assuming 50% of power is used in heating the machine? Specific heat of aluminum = 0.91 kJ/kg°C

A 10 kW drilling machine is used to drill a bore in a small aluminum block of mass 8 kg. How much is the rise in temperature (in °C) of the block in 2.5 minutes, assuming 50% of power is used in heating the machine? Specific heat of aluminum = 0.91 kJ/kg°C Correct Answer 103

Concept:

Heat absorbed by aluminum block:

δQ = mcΔT

Calculation:

Given:

Power of the machine, P = 10 kW

Now,

As 50% of power is used in heating

∴ Heat generated = 0.5 P = 5 kW = 5 kJ/s

Heat generated in 2.5 min (i.e 150 s),

∴δQ = 5 × 150 = 750 kJ

Heat absorbed by aluminum block:

δQ = mcΔT

750 = 8 × 0.91 × ΔT

ΔT = 103°C

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