You need boiling water to make your morning coffee, but your coffee maker is not

Question

You need boiling water to make your morning coffee, but your coffee maker is not working. You decide to put the 300 mL of water into a thermos and shake it up and down to transform mechanical energy into thermal energy.

(a) If the water starts at a temperature of 15 C, how much energy must you add to bring it to its boiling point?

(b) If the water in the thermos effectively falls a vertical distance of 0.5 m with each shake, how many shakes will it take to heat the water?

(c) If you make 100 shakes every minute, how long will it take to heat the water? Give your answer in minutes and/or hours.

Equations:
Q=m*c*(deltaT)
Cwater = 4186 J/(kg?C)

Explanation / Answer

Part A)

Apply Q =mc(delta T)

Q = (.300)(4186)(85)

Q = 106743 Joules

Part B)

Q = PE = xmgh

106743 = x(.300)(9.8)(.5)

x = 72614 shakes

Part C)

72614/100 = 726.14 minutes

That is 12.1 hours

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