Specific heat capacity and friction

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SUMMARY

The discussion focuses on calculating the number of complete revolutions required for a rotating metal drum to increase its temperature by 5.0 K, given a tangential frictional force of 20N and a specific heat capacity of 0.35 kJ/kg K. The correct formula to use is Q = mcΔT, where Q represents heat energy, m is mass, c is specific heat capacity, and ΔT is the temperature change. The calculation reveals that the number of revolutions is determined by dividing the distance traveled by the circumference of the drum, not the radius. The final answer is 140 revolutions.

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chanella35
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1. The tangential frictional force exerted by a band brakes on a rotating metal drum of circumference 0.25m is found to be 20N. If the mass of the drum is 0.4kg and its specific heat capacity is 0.35 kJ/kg K, calculate the number of complete revolutions of the drum are required to increase its temperature by 5.0 K.

Q= mcT
W=F*d

my attempt:

Q= mc[delta]T
W=F*d

f*d=mcT
20*d=400g*0.35*5
20d= 700
d=35
revolutions = 35/.25=140 or 1.4*10^2



^^^^^is that correct?
 
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chanella35 said:
revolutions = 35/.25=140 or 1.4*10^2
^^^^^is that correct?
No. If you have d, the number of revolutions is not d divided by the radius. It is d divided by the circumference. Also, it is a good habit to show the appropriate units every time you write down a number unless the number is dimensionless.
 

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