freefall (1 Viewer)

[zeropoint]

Originally posted by xiao1985
edit: i fink as far as hsc is concerned, yes s/he is in non-inertial frame of reference.

I don't know how the board of studies feels about this, but I'd strongly argue against that statement.

 

[xiao1985]

Originally posted by zeropoint
I don't know how the board of studies feels about this, but I'd strongly argue against that statement.

uhm interestin... may i hear the rest of teh story??? i found ur previous argue ment (the one abt person a the lift and person b in a space not affected by any mass) is rather... i dunno... if dat was true, doesn't that mean there will be no non inertial frame of reference??

 

[zeropoint]

A person inside a spacecraft accelerating at 9.8 m/s^2 can carry out a simple experiment using a mass on a spring to distinguish themselves from rest. The mass will displace from the equilibrium position by an amount proportional to the acceleration of the spacecraft. A person in free fall who performs the same experiment will observe zero displacement, as would an observer in free space.

 

[xiao1985]

true ey... i was thinkin abt that when writin the last thread... that is true eh?? u convinced me... ^^

 

[gordo]

yes it would be in an inertial frame of reference, the rock iteself is accelerating within the inertial frame of reference, it can do whatever it likes.

 

[doodydo]

I'll tell you all the answer if you're all confused-
non-inertial!

 

[Zarathustra]

Wasn't there this famous Gedanke(n) by Einstein where he propsed that you couldn't tell the difference between gravity in a stationary lift or a lift which is being accelerated upwards at 9.8m^-2 which is situated in an area unaffected by gravity (impossible as has already been mentioned in this thread) so wouldn't free fall be 'g' minus 'g' whereas the spaceship would just be 'g' and that stationary objects on Earth would be in non-inertal frames?

 

[Maianbarian]

with the person in the lift, they are in an inertial frame of reference if they have reached terminal velocity because at this point they are not accelerating. Sure they have the earth accelerating them towards the centre but they also have friction applying an equal and opposite force. Hence total force = 0

F=m.a
a=F/m
a=0/m
a=0

therefore inertial.

 

[xiao1985]

Originally posted by Maianbarian
with the person in the lift, they are in an inertial frame of reference if they have reached terminal velocity because at this point they are not accelerating. Sure they have the earth accelerating them towards the centre but they also have friction applying an equal and opposite force. Hence total force = 0

F=m.a
a=F/m
a=0/m
a=0

therefore inertial.

uhm, dat logic is abit weird... i fink you assume no friction for this question... if there is friction, then the person in the lift would be in noninterntial frame of reference... because there are tests dat can be done to distinguish him/her from a person inaffected by any gravity...

 

[Xayma]

If you think in terms of g-forces it can be shown that it is inertial.

Assume that you were in space and unaffected by gravity you would have 0 g-forces.

Now
g-forces=(g+a)/(g)
=9.8-9.8/9.8=0

Hence there can be no test done to distinguish between the two frames.

 

[xiao1985]

yes xayma... but a fwnd put fwd an interestin arguement: wut if u shoot a photon??