A body of mass 1 kg tied to a string is just able to move in a vertical circular path of the radius 1 m .…

A body of mass 1 kg tied to a string is just able to move in a vertical circular path of the radius 1 m. The difference between the kinetic energies at its highest and lowest positions of the body is
  1. $4\sqrt{5}J$
  2. $20J$
  3. $10J$
  4. $30J$

Solution

Kinetic energy is the energy possessed by a body of mass m due to its velocity v.

KE=12mv2



At the highest point velocity, vA=rg

   KE=12mvA2

At the lowest point velocity, vB=5 rg

KE=12mvB2

Difference n KE=12mvB2-vA2=12m5 rg-rg

=2mrg=2×1×1×10=20 J

Asked in: MHT CET Full Test 2

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