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Question
A brick weighing 4.0 kg is dropped into a 1.0 m deep river from a height of 2.0 m. Assuming that 80% of the gravitational potential energy is finally converted into thermal energy, find this thermal energy is calorie.
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Solution
Given:-
Mass of the brick, m = 4 kg
Total vertical distance travelled by the brick, h = 3 m
Percentage of gravitational potential energy converted to thermal energy = 80
Total change in potential energy of the brick = mgh = 4 × 10 × 3 = 120 J
`"Thermal Energy"=120xx80/100=96 J`
Thermal energy in calories is given by
`U=96/4.2=22.857"cal"approx23"cal"`
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