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A 5000 kg rocket is set for vertical firing. The exhaust speed is 800 m/s. To give an initial upward acceleration of 20 m/s 2 , the amount of gas ejected per second to supply the needed thrust will be (Take g = 10 m/s 2 ) (a) 127.5kg/s (b) 137.5kg/s (c) 155.5 kg/s (d) 187.5 kg/s



A 5000 kg rocket is set for vertical firing. The exhaust speed is 800 m/s. To give an initial upward acceleration of 20 m/s2, the amount of gas ejected per second to supply the needed thrust will be (Take g = 10 m/s2)


        (a)    127.5kg/s  


(b)    137.5kg/s


        (c)    155.5 kg/s


(d)    187.5 kg/s


Grade:upto college level

5 Answers

Simran Bhatia
348 Points
10 years ago

(d)

Given: Mass of rocket (m) = 5000 Kg Exhaust speed (v) = 800 m/s Acceleration of rocket (a) = 20 m/s2

Gravitational acceleration (g) = 10 m/s2

We know that upward force

F = m (g + a) = 5000 (10 + 20)  

= 5000 × 30 = 150000 N.

We also know that amount of gas ejected

 

Aswin M
17 Points
5 years ago
Mass of rocket(M)= 5000 kg
Exhaust speed(v)=800m/s^2
Acceleration(a)=20m/s^2
acceleration due to gravity (g)=10 m/s^2
F=m(g+a)=5000(10+20)=15000N
amount of gas ejected per second= F/v=15000/800=187.5 kg/s
Thank you!!!
Aayan Ta
28 Points
5 years ago
:GivenMass of rocket(m)= 5000 kgExhaust speed(v)=800m/s^2   :FormulaAcceleration(a)=20m/s^2​v(dm/dt)=m(a+g)
Solution: 
800(dm/dt)=5000(20+10
dm/dt= 187.5kg/s
Sivaneeth R
15 Points
4 years ago
We know that F=m(g+a)
=5000(10+20)
=5000×30
=150000N
 
Amount of gas ejected per second=F/V
150000/800
=187.5kg/s
=150000/800
 
Rishi Sharma
askIITians Faculty 646 Points
3 years ago
Dear Student,
Please find below in the attached image solution to your problem.

Thanks and Regards
645-772_01.PNG

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