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A rocket is going upwards with accelerated motion. A man sitting in it feels his weight is increased 5 times his own weight. If the mass of the rocket including that man is 1x10^4kg. How much force is being applied by rocket engine.

A rocket is going upwards with accelerated motion. A man sitting in it feels his weight is increased 5 times his own weight. If the mass of the rocket including that man is 1x10^4kg. How much force is being applied by rocket engine. 

Grade:12th pass

3 Answers

Arun
25750 Points
4 years ago
First, find the acceleration of the rocket. Then, multiply it with the whole weight of the system.
You will get answer as 5*( 10^5 ).
 
Hope it helps
 
Regards
Arun (askIITians forum expert)
 
Piyush Kumar Behera
417 Points
4 years ago
The first concept is that the normal reaction on the man is actually the measured weight of the man.
The man when sits on the accelerated rocket,means that the man is accelerating with the rocket.
 
So we can approach the question by drawing the free body diagram of the man.
 
Net force upwards is the normal N acted by the rocket on the man.
And the weight W is the only downward force acting on the man.
W = mg
But N = 5W 
which means by newtons law
 
N – mg = ma
5mg – mg = ma
a = 40m/s^2
 
assuming g = 10 m/s^2
 
Net force on the rocket is (mass of rocket + man) x a = 1000 x 40 Newton = 40000 Newton.
Which is our required answer.
 
I hope it clears!!
 
Piyush Kumar Behera
IIT Dhanbad
 
 
                  
 
 
Piyush Kumar Behera
417 Points
4 years ago
Sorry in the above Solution there was a mistake.
This is corrected one.
 
The first concept is that the normal reaction on the man is actually the measured weight of the man.
The man when sits on the accelerated rocket,means that the man is accelerating with the rocket.
 
So we can approach the question by drawing the free body diagram of the man.
 
Net force upwards is the normal N acted by the rocket on the man.
And the weight W is the only downward force acting on the man.
W = mg
But N = 5W 
which means by newtons law
 
N – mg = ma
5mg – mg = ma
a = 40m/s^2
 
assuming g = 10 m/s^2
 
Net force on the rocket is (mass of rocket + man) x a = 10000 x 40 Newton = 400000 Newton.
Which is our required answer.
 
I hope it clears!!
 
Piyush Kumar Behera
IIT Dhanbad

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