2015 HSC Multiple choice Q19 (1 Viewer)

[leehuan]

Just going through my mistakes to see where I lost marks.

An astronaut working outside a spacecraft in orbit around Earth is not attached to it.
Why does the astronaut NOT drift away from the spacecraft?

(A) The force of gravity acting on the astronaut and spacecraft is negligible.
(B) The spacecraft and the astronaut are in orbit around the Sun with the Earth.
(C) The forces due to gravity acting on both the astronaut and the spacecraft are the same.
(D) The accelerations of the astronaut and the spacecraft are inversely proportional to their respective masses

And I'm unsure about this one. Can someone please explain?

 

[Nailgun]

C is wrong because the forces on the astronaut and the craft are different

A is not true because the force is significant enough to act as centripetal force

B and D are true statements

D is the answer because as the astronaut is detached from the system, the acceleration on him increases as the mass of decreases, maintaing the same flight path

 

[leehuan]

Fair point. It seems like I forgot the definition of force for a moment and misplaced it with acceleration, therefore C must be wrong..

However the inverse proportion doesn't seem to explain enough for me. What about the acceleration ensures that they will be in the same flight path when the velocity can be altered due to varying accelerations?

I colour-coded for a reason. I knew A was false and B was unrelated.

EDIT: Nvm, I completely forgot that g is a constant. Ok thanks.

 

[Nailgun]

Ah lol, I thought you color-coded what your answer was and what the actual answer was

 

[wu345]

My teacher said B is wrong because the astronaut and spacecraft aren't orbiting the sun; they're orbiting the Earth (read the question again)

 

[Nailgun]

From the frame of reference of the sun, the astronaut and spacecraft are orbiting it