JEE Main Physics question
A 5000 kg rocket is set for vertical firing. The exhaust speed is 800 ms⁻¹. To give an initial upward acceleration of 20 ms⁻², the amount of gas ejected per second to supply the needed thrust will be (take g = 10 ms⁻²) [UP SEE 2009, OJEE 2009]
Answer: (B)
Solution
Required thrust = m(g+a) = 5000(10+20) = 150000 N. dm/dt = Thrust/ = 150000/800 = 187.5 kg s⁻¹.