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Most Important Selected Qs for JEE AdvancedPhysicsGravitation

Two objects of mass m and 4 m are at rest at an infinite separation. They move towards each other under mutual attraction. If G is the universal gravitational constant. Then at separation r .

Options

  1. AThe sum of energy of the two objects is negative.
  2. BTheir relative velocity of approach is ( 10 G ~m r )^ 1 / 2 in magnitude
  3. CThe sum of kinetic energy of the objects is 4 Gm ^2 r .
  4. DThe sum of angular momenta of both the objects is zero about any point.

Correct answer

D. The sum of angular momenta of both the objects is zero about any point.

Step-by-step solution

Initially potential and kinetic both energies zero and from conservation of mechanical energy total energy of the two object zero Further, decrease in P.E. = increase in K.E. aligned & G(m)(4 m) r = 1 2 v_r^2 & v_r= 10 G m r & Total K.E. = G(m)(4 m) r = 4 G m^2 r aligned

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