a. Concrete has a specific heat capacity of 670 joules/kg-oC. A 2kg concrete blo

Question

a. Concrete has a specific heat capacity of 670 joules/kg-oC. A 2kg concrete block, that has a temperature of 20oC, is dropped from a height of 100 meters. What is its temperature after it hits the ground if it lost no heat to the surrounding environment?

b. Referring to the above problem, the block is now raised back to 100meters without losing or gaining heat from the environment. What is the block's temperature after it was raised?
Answer:
a. 20o C, the same as it was before it fell.
b. This can't be determined.
c. The same as it was after it fell.
d. Less than it was after it fell

Explanation / Answer

Concrete specific heat capacity c = 670 joules/kg o C

Mass of  concrete block m = 2 kg

Initial temperature t = 20 o C

Initial height h = 100 meters

Potential energy at height h is U = mgh

                                                = 1960 J

Amount of heat taken by block Q = U

                                         mcdt = 1960

From this raise in temprature dt = 1960 / mc

                                                = 1.462 o C

Temperature after it hits the ground if it lost no heat to the surrounding environment t ' = t + dt

         t ' = 21.462 o C

(b).20 degrees C that same as it was before it fell

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