Work done by friction produces heat. That\'s why we rub our hands together when

Question

Work done by friction produces heat. That's why we rub our hands together when they're cold... Suppose that you rub your hands back-and-forth a total of 23 times while exerting an average frictional force of magnitude 51.3 N. In doing so, you managed to warm 0.11 kg of tissue, mostly in the palms and fingers. (a) How much work was done by friction if each back-and-forth motion corresponds to a distance of 7.5 cm? Work = J (b) How much did the temperature of the warmed tissue increase if it absorbed all of the heat generated by friction? Use c = 3500 J/kg·K for the specific heat capacity of the hand tissue. T = °C

Explanation / Answer

here,

frictional force , ff = 51.3 N

mass of tissue , m = 0.11 kg

number of times , n = 23

(a)

distance , d = 7.5 cm = 0.075 m

the work done , W = ff * ( d * n)

W = 51.3 * 0.075 * 23

W = 88.49 J

work was done by friction is 88.49 J

(b)

let the change in temprature be delta T

W = m * delta T * c

88.49 = 0.11 * delta T * 3500

delta T = 0.23 degree

the raise in temprature is 0.23 degree

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