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

=>  

most voltage drop calculators want the distance between the source and destination. then internally, they double it so both the source and return wires are calculated. but you need to know which distance the calculator uses so you're not half of what you should be or double what you should be.

most circuit breakers will not take a #6 directly, so the electrician will have to splice on a smaller pigtail. you also have to upsize the grounding wire when you upsized the ungrounded (hot) wire (see note in 250.122). this will preclude using most cable assemblies, as a cable with #6 copper will most likely only have a #10 grounding conductor. you need a #6 grounding conductor if the circuit is 20a. a #8 cable is no better, as it will have a #10 grounding conductor too. but most 20a breakers will take a #8 directly.

in your related post, you didn't say what type of load this is. if it is a light or heater, voltage drop won't be a big issue. if this is a motor, the current needs are huge at startup and the voltage drop can pose a problem. if this is a motor, knowing if the motor is under much load during startup will answer the voltage drop effect (a saw is easier to start than a compressor).