Answers

2014-01-29T14:00:28+05:30
A nail becomes warm when hammered into a plank because continous hitting of hammer warms the nail. 
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2014-01-29T16:44:27+05:30
A nail becomes warm when hammered into a plank be cause every time the hammer hits the nail, the kinetic energy of the hammer gets transferred into the nail. this energy transfer is seen through the motion of the nail into the plank, the sound that is created every time the nail is hammered and the heat produced, i.e., the nail becoming warmer.
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