HSC Physics Space (1 Viewer)

[apurba]

Analyse the changing acceleration of a rocket during launch in terms of the:
- Law of Conservation of Momentum
- Forces experienced by astronauts

What exactly do we need to know for this dot point?

 

[Mr_Kap]

I don't know. Someone help!

 

[Drsoccerball]

Momentum = mass x velocity

Since momentum is constant according to the law of conservation of momentum as mass decreases(fuel is lost) velocity must increase and therefore acceleration also increases as acceleration is change in velocity over a specific period of time.

=ma

As the mass of the rocket decreases the acceleration increases since force is constant.

 

[Kaido]

Define conservation of momentum briefly, Newton's third law F1=-F2 is appropriate in this case.
Let F1=gas propulsion, F2=Force acting on rocket. From F=ma, we know that acc increases as m decreases and F remains constant (for HSC sake). Clearly, momentum is conserved.
Forces experienced can be regurgitated as usual, except, you want to mention that g-force INCREASES as acc increases

 

[apurba]

Do we need to know about the multi-stage rocket system? Like the different stages and stuff and how the engine throttles, since the dot point specifically says "during launch?"

 

[astroman]

Do we need to know about the multi-stage rocket system? Like the different stages and stuff and how the engine throttles, since the dot point specifically says "during launch?"

Yes it's fairly simple though, when the rocket intially starts, the g forces accelerate, then when the second stage detaches, the rockets are throttled down so g-forces are brought down, then increased again as stage two rockets deploy, this goes on until all launch stages have been deployed. Graph look's like this, may have to draw in an exam.

 

[Mr_Kap]

Can anyone explain g-forces to me and any equations i have to know relating to this?

 

[astroman]

Can anyone explain g-forces to me and any equations i have to know relating to this?

may have to calculate g-force experienced, formula is: (g+a)/9.8

 

[iforgotmyname]

^ you can derive it

G force= apparent weight/actual weight
= (mg+ma)/mg cancel out the m and insert g=9.8 and ur done.

Btw you can have negative g force when accelerating downwards

 

[Drsoccerball]

^ you can derive it

G force= apparent weight/actual weight
= (mg+ma)/mg cancel out the m and insert g=9.8 and ur done.

Btw you can have negative g force when accelerating downwards

What if the acceleration downwards is twice or more than twice the acceleration due to gravity?
Edit: My bad i thought said can't

 

[Kaido]

What about the formula for the force acting on astronaut due to their couch/chair
Also, differentiate between weightless and weightlessness