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Concepts Of Physics MCQ Edition [Volume 1]PhysicsGravitation

A person transports a mass of 1 kg from infinity to a point A . The mass is initially at rest, but it attains a speed of 2 m/s upon reaching A . If the work done by the person on the mass is -3 J , the potential at point A is

Options

  1. A-1 J/kg
  2. B-3 J/kg
  3. C-5 J/kg
  4. D-2 J/kg

Correct answer

C. -5 J/kg

Step-by-step solution

According to the work-energy theorem, the total work done on the mass is equal to the change in its kinetic energy. W_ ext + W_ grav = K Since the work done by the gravitational force is the negative of the change in potential energy, W_ grav = - U . W_ ext - U = K W_ ext = K + U Given W_ ext = -3 J , m = 1 kg , v_i = 0 , and v_f = 2 m/s . K = 1 2 mv_f^2 - 1 2 mv_i^2 = 1 2 1 (2)^2 - 0 = 2 J U = m(V_A - V_ ) = 1 (V_A - 0) = V_A Substituting the values into the equation: -3 = 2 + V_A V_A = -5 J/kg

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