A 50 kg bag of sand ar 25 degree C falls 10 m onto the pavement and comes to an

Question

A 50 kg bag of sand ar 25 degree C falls 10 m onto the pavement and comes to an abrupt stop. Neglect any transfer of heat betweeen the sand and the surroundings and assume that the thermal heat capacity of the snad is so large that its temperature is unchanged.

a) What is the dissapative work done on the sand?

b) what is the change of the internal energy of the sand?

c) What is the entropy change associated with this change in U at constant T?

    (The sand does no work as it deforms when it hits the pavement, only its shape changes, not its volume)

Please show work

Explanation / Answer

a)dissipative work done = change in kinetic energy on striking = potential energy at top

= mgh = 50 *9.8*10 = 4900 J

b) Change in internal energy = 0 as temperature is unchanged

c) change in entropy = 4900 /298 = 16.44 J/K

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