2. A rocket, with an initial mass of 800 kg, is to be launched vertically. Upon ignition the rocket consumes fuel at the rate of 5 kg/s and ejects gas at atmospheric pressure with a speed of 3500 m/s relative to the rocket. Determine the initial acceleration of the rocket and the rocket speed after 20 s if air resistance is neglected. [40 20 points].

The acceleration is  

The velocity after 20 second is  

Explanation:

From the question  we are told that

    The mass of the rocket is  

     The rate of fuel consumption is  

      The  speed of  speed at which gas is ejected at atmospheric pressure is  

Generally the thrust force (the force propelling the rocket) is mathematically represented as

=>      

=>      

Generally the net force acting on the rocket is mathematically represented as

=>      

=>      

=>    

Generally the rocket speed is mathematically represented as

Here   is the initial velocity of the rocket which is  0 given that it started from rest

of the rocket after fuel has been consumed for time t =  20

second, this mathematically represented as

=>    

=>    

So

=>