Physics 12.29 ex 4

Question

A cup of water is heated with a heating coil that delivers 130W of heat. In one minute, the temperature of the water rises by 21 degrees C. What is the mass of the water?

Answer 1

Power delivered = 130 watts = 130 joules/sec.

Therefore, in one minute, the total energy from the heating coil =

130 joules/sec * 60 sec/min * 1 min = 7800 joules

This is the total energy absorbed by the water. Hence,

7800 = MCp(delta T)

where

M = mass of the water

Cp = specific heat of water = 4.184 J/g C (constant)

delta T = temperature change = 21 C (given)

Substituting values,

7800 = M(4.184)(21)

Solving for M

M = 7800/(4.184 * 21)

M = 88.77 grams