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KCET2018PhysicsWork, Power and Energy

A mass ' ( m ) ' on the surface of the Earth is shifted to a target equal to the radius of the Earth. If ' ( R ) ' is the radius and ' ( M ) ' is the mass of the Earth, then work done in this process is

Options

  1. A( m g R 2 )
  2. BmgR
  3. C( 2 ) mgR
  4. D( m g R 4 )

Correct answer

A. ( m g R 2 )

Step-by-step solution

Gravitational potential energy on surface on Earth is [ U_ E = -G M m R ] where ( M ) is mass of Earth; ( m ) is mass on surface of Earth; ( R ) is radius; ( G ) is gravitational constant When mass ( m ) is shifted to a target then potential energy is [ U= -G M m (R+R) = -G M m 2 R ] Work done in the process is [ array l W=U-U_ E =- G M m 2 R - (- G M m R )=- G M m 2 R + G M m R W= G M m 2 R array ] Now substitute ( G M=g R² ), we get [ W= g R² m 2 R = g R m 2 ] Therefore, work done in process ( = m g R 2 )

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