Physics Space Topic

[shreya_ajoshi]

Hi!
How do you do this question?
1a) A rocket has a mass of 400kg. 75% being fuel. It develops a thrust of 8000N. Calculate its initial acceleration

Thank you!!!

[RuiAce]

Hi!
How do you do this question?
1a) A rocket has a mass of 400kg. 75% being fuel. It develops a thrust of 8000N. Calculate its initial acceleration

Thank you!!!

[kiwiberry]

wait, does the net force on the rocket need to include the weight force as well?

so Fnet = ma
T - mg = ma
a = (T-mg)/m
= ( 8000-400x9.8 )/400
= 10.2 ms^-2

[RuiAce]

Oh, no wonder I got a weird result. I can't do simple arithmetic.

[shreya_ajoshi]

Thank you!!
So the '75% being fuel" has nothing to do with the question?

(Answer: Yes)

[shreya_ajoshi]

Hi
Part b) of the same question asks
"Calculate its acceleration when half its fuel has been consumed"


Actually, don't worry. I got the answer
Thanks anyways


Actually how do you do this
c) Calculate the g-force on a 60kg astronaut in the rocket when half the fuel has been consumed. Assume the rocket is still within Earth's gravitational field. The acceleration of the rocket when half the fuel is consumed is 22.2ms^-2

Mod edit: Merged duplicate posts. At times like this, please resort to the modify button instead of posting multiple times.

[jamonwindeyer]

Hi
Part b) of the same question asks
"Calculate its acceleration when half its fuel has been consumed"


Actually, don't worry. I got the answer
Thanks anyways


Actually how do you do this
c) Calculate the g-force on a 60kg astronaut in the rocket when half the fuel has been consumed. Assume the rocket is still within Earth's gravitational field. The acceleration of the rocket when half the fuel is consumed is 22.2ms^-2

Mod edit: Merged duplicate posts. At times like this, please resort to the modify button instead of posting multiple times.

Hey! So for this question, we just need to figure out how much extra acceleration the astronaut is experiencing! The astronaut is travelling upwards with an acceleration of 22.2 metres per second per second, and the astronaut experiences an extra 1G of force for every 9.8 metres per second per second of acceleration upwards (due to the reaction forces).



So, the astronaut experiences 2.265 G's of extra forces due to the rockets motion. Add this to the normal 1G of weight force, and you get 3.265G

Hope this helps!