**AP Physics Ch 13**

**Problems with Heat, Mechanical Energy**

1. In order to raise the temperature of 1.0 kg of a substance
from 0^{o}C to 100^{o}C, 47,000 J of heat are
needed. What is the specific heat of the substance? What is the
substance?

2. How much heat is given off when 0.5 kg of water is cooled
from 110^{o}C to -10.0^{o}C?

3. If all the potential energy of a waterfall 100 m high is converted into thermal energy, what is the temperature difference between the top and bottom of the falls?

4. If 10.0 g of water at 20^{o}C is poured into 100 g
of water at 80^{o}C, what is the final temperature?

5. A 100 g sample of an unknown metal at a temperature of 95^{o}C
is poured into a 140 g aluminum calorimeter containing 200 g of
water. If the initial temperature of the water and calorimeter
was 16^{o}C and the final temperature was 20^{o}C,
find the specific heat of the unknown metal.

6. What must be the initial velocity of a silver (Ag) bullet
at a temperature of 20^{o}C so that the heat developed
when it is brought to a complete stop shall be sufficient to melt
it?

7. How much steam at 100^{o}C is required to melt 1.0
kg of ice at 0^{o}C?

8. A 1500 W heater is submerged into 1 kg of water that is
well below 100^{o}C. At what rate, in ^{o}C/s,
does the temperature rise when the heater is operating at its
rated power?

9. An automobile having a mass of 1900 kg and traveling at a speed of 30 m/s is braked smoothly to a stop without skidding in 15 s.

a) How much energy is dissipated in the brakes?

b) What is the average power delivered to the brakes during stopping?

c) If the total heat capacity of the braking system is 3000 J/^{o}C, what is the temperature rise of
the brakes during the stop?

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