A rocket of mass m = 20 kg has M = 180kg fuel. The uniform exhaust velocity of the fuel is v r = 1.6 km/s.
(i) Calculate the minimum rate of consumption of fuel so that the rocket may rise from the ground.
(ii) Also calculate the maximum vertical speed gained by the rocket when the rate of consumption of fuel
μ is (g = 10 m/s 2 ) & ( λ n 10 = 2.30)
Text Solution
Verified by ExpertsCHECK THE SOLUTION.
(i) 
= 1.25 kg/s,
(ii) 
2.8 km/s, 3.6 km/s.
Sol. m 0 = 20 kg ; m = 180 kg.
– F th = (m +M)g = 2×10 3 N
– F th = v r 
So 
= 
= 1.25 kg/s. Ans.
v = v r λ n 
– gt.
(i) t 1 = 
= 
= 90 s.
∴ v 1 = 1600 λ n 
– 10 × 90
v 1 = 2.784 km/s. Ans.
(ii) t 2 = 
= 
= 9s.
v 2 = 1600 λ n 
–10 × 9
v 2 = 3.59 km/s. Ans.
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