JEE Main20211 Sep 2021Evening ShiftPhysicsWork, Power and EnergyActual
An engine is attached to a wagon through a shock absorber of length 1 . 5   m . The system with a total mass of 40 , 000   kg is moving with a speed of 72   km   h - 1 when the brakes are applied to bring it to rest. In the process of the system being brought to rest, the spring of the shock absorber gets compressed by 1 . 0   m . If 90 % of energy of the wagon is lost due to friction, the sp
Correct answer
16
Step-by-step solution
Work = Δ K . E . W triction  + W spring  = 0 - 1 2 m v 2 - 90 100 1 2 m v 2 + W spring  = - 1 2 m v 2 w spring  = - 10 100 × 1 2 m v 2 - 1 2 k x 2 = - 1 20 m v 2 ⇒ k = 40000 × ( 20 ) 2 10 × ( 1 ) 2 = 16 × 10 5