AP EAMCET201921 Apr 2019Evening ShiftPhysicsWork, Power and EnergyActual
A body is released from a height of 30 m vertically downwards. The speed of the body at which potential energy is twice that of kinetic energy is (Acceleration due to gravity = 10 m s - 2 )
Options
- A20 2   m   s - 1
- B10 2   m   s - 1
- C10   m   s - 1
- D20   m   s - 1
Correct answer
B. 10 2   m   s - 1
Step-by-step solution
Suppose at velocity v ,potential energy of body is twice that of kinetic energy. Using energy conservation- m g H = K E f + P E f     … 1 Since P E f = 2 × K E f Put this value in equation 1 - m g H = 3 × K E f ⇒     m g H = 3 × 1 2 m v 2 ⇒     v = 2 3 g H ⇒     v = 10 2     m   s - 1