Question
Wed March 28, 2012 By:
 

A body of mass 1 kg is thrown upwards with a velocity 20 m/s. It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction? (1)10 J (2)20 J (3)30 J (4)40 J

Expert Reply
Tue April 03, 2012

The initial kinetic energy of the 1 kg mass is given by

½ mv2 = ½ ×1×202 = 200 J.

The gravitational potential energy of the 1 kg mass at its maximum height is given by

Mgh = 1×10×18 = 180 J.

The energy lost due to air friction is therefore equal to 200 – 180 = 20 J.

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