Question

A two stage rocket weighs 100 kg and 10 kg and contains 800kg and 90 kg fuel
respectively, Find the final velocity at the end of the second stage if the exhaust velocity
is 2 km/sec.

Answer 1

Answer:

The answer is 7.82 X 10^3 m/s.

Explanation:

The initial velocity of the rocket V0 = 0

Velocity of the rocket after exhaustion of the forst stage is  

         V = μ ln m0 / m

Here,  

m0 = 100 + 10 + 800 +90 = 1000 kg

m =  100 + 10 + 90 = 200 Kg

Thus |V| = 2 ln 5

            = 2 x 1.609

            = 3.218 Km/s

The second stage becomes operative when the first is detached from it.

   μ0 = 3.218 Km/s

   m0 = 10 + 90 = 100 Kg

   m = 10 Kg

Thus, |V| = 3.22 + 2ln (100 /10)

             = 3.22 + 2 X (2.3)

             = 7.82 X 10^3 m/s

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Answer 2

Answer:

Explanation:

we know that f=ma

since acceleration(a) = speed of exhaust = 2km/sec

and m=mass = weight/gravitational acceleration

and since weight of rocket = 1000kg, therefore mass = 102 approx

therefore force  = ma

=2*102 km/sec

=204000 N

therefore force acting on the rocket = 204000N

i got stuck here. sorry