Question

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 surrounding? Specific heat of aluminium `= 0.91 J//g^(@)C`.
A. `103^@C`
B. `130^@C`
C. `105^@C`
D. `30^@C`

Answer 1

Correct Answer - A
Total work done by drill machine in `2.5xx60s`
`=(10xx10^3)(2.5xx60)=15xx10^5J`
Energy lost `=50%` of `15xx10^5J=7.5xx10^5J`
Energy taken by its surroundings, i.e., aluminium block
`DeltaQ=mcDeltat=8xx10^3xx0.91xxDeltaTJ`
Energy given `=`Energy taken
`7.5xx10^5=8xx10^3xx0.91xxDeltaT`
`impliesT=103^@C`