- #1
Rapid A
Homework Statement
https://isaacphysics.org/questions/gcse_ch2_13_q10
https://www.physicsforums.com/attachments/213735
The thrust generated by a rocket engine is equal to the mass of propellant burnt each second multiplied by the exhaust velocity of the gas. The Space Shuttle (with booster rockets and external tank) had a total mass of 2 040 000 kg at launch. In this question we shall assume that the exhaust velocity of the gas was 3 000 m/s
https://www.physicsforums.com/attachments/213736
My problem here is that I've tried my best in solving this but it won't accept my answer of 20400. I've tried other methods which gave me answers like 61200.
2. Homework Equations
Acceleration = Resultant Force / Mass of Object
Thrust = Mass of propellant burnt/s x Exhaust velocity of gas (m/s)
The Attempt at a Solution
Since I'm supposed to work out the mass of propellant burnt per second, I did:
- Thrust = 20 400 000 N
- Velocity of gas = 3 000 m/s
Mass of propellant burnt = 6800 kg
I worked out the mass of propellant burnt per second for lift off; so to work out the mass of propellant burnt per second to make the rocket accelerate at '3g' (i.e 30 m/s2) I tried multiplying 6800 by 3 (20400), by 30 (204000), by 9 (61200), by 900 (6120000) and none of them seem to be the right answer.
For lift off I sort of guessed so I'm not sure of the formula I've used. It would be helpful if I was given the formula to use and some assistance on working out the answer to part B of the question. To test the question on the website, here's the link:
https://isaacphysics.org/questions/gcse_ch2_13_q10
and please let me know if you've managed to get the right answer.