JEE Main202623 January 2026Morning ShiftPhysicsWork, Power and EnergyActual
A small bob A of mass m is attached to a massless rigid rod of length 1 m pivoted at point P and kept at an angle of 60^ with vertical as shown in figure. At distance of 1 m below point P , an identical bob B is kept at rest on a smooth horizontal surface that extends to a circular track of radius R as shown in figure. If bob B just manages to complete the circular path of radius R upto a point Q after being hit elas
Options
- A1 5
- B2- 3 5
- C3 5
- D2+ 3 5
Correct answer
A. 1 5
Step-by-step solution
Bob A swings from 60° to vertical. Height drop h = l(1- 60°) = 1 0.5 = 0.5 m. Velocity of A at bottom: v_A = 2gh = 2 10 0.5 = 10 m/s. Elastic collision between equal masses: B gets v_B = 10 m/s, A stops. For B to just complete circular loop: v_B^2 = 5gR . 10 = 5 10 R R = 1 5 m.