JEE Main202126 Aug 2021Morning ShiftPhysicsLaws of MotionActual
The initial mass of a rocket is 1000 kg . Calculate at what rate the fuel should be burnt so that the rocket is given an acceleration of, 20 m s - 2 . The gases come out at a relative speed of 500 m s - 1 , with respect to the rocket: Use g = 10 m s - 2
Options
- A10   kg   s - 1
- B60   kg   s - 1
- C500   kg   s - 1
- D6 . 0 × 10 2   kg   s - 1
Correct answer
B. 60   kg   s - 1
Step-by-step solution
Here we are applying the equation, F r − m g = m a From Newton's second law, F r = d m d t v r ⇒ d m d t v r = m g + m a Put the given values in the above equations, ⇒ d m d t 500 = 1000 ( 10 + 20 ) ⇒ d m d t = 60   kg   s - 1 .