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Motion In Straight Line

Question
CBSEENPH11020721
Wired Faculty App

A body mass 1 kg is thrown upwards with velocity 20 ms-1. It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction?  (g = 10 ms-2)

  • 20 J

  • 30 J

  • 40 J

  • 10 J

Solution

A.

20 J

The energy lost due to air friction is equal to the difference of initial kinetic energy and final potential energy.
Initially, body possess only kinetic energy and after attaining a height the kinetic energy is zero.
Therefore, loss of energy = KE - PE
=1 half mv squared minus mgh equals space 1 half space straight x 1 space straight x space 1400 space minus 1 space straight x space 18 space straight x space 10 space equals space 200 minus 80 space straight J space equals space 20 space straight J 1 half mv squared minus mgh equals space 1 half space straight x 1 space straight x space 1400 space minus 1 space straight x space 18 space straight x space 10 space equals space 200 minus 80 space straight J space equals space 20 space straight J

Some More Questions From Motion in Straight Line Chapter

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