# Apparent weight problem (kinematics + conservation of Energy + Newton's laws)

• simphys
In summary: Actually, it is sufficient that ##v_3## is big enough for the coaster to go around. Negative ##F_3## would imply hanging from the top of the loop instead of being pressed into the track. Now, I don’t know if any roller coasters are actually constructed to provide negative gs in loops, but I believe roller coaster cars should be able to stay on track even with negative g for safety...
simphys said:
Erobz do you know about the tangential and normal components aka n-t axes(for curvilinear motion)
it states that the positive normal axis (perpendicular to the tangential axis) is always towards the concave inside and thus towards center of curvature where in this case this center of curvature is constant as the motion itself is a circle.
I may have known that 15 years ago..."If you don't use it, you lose it" is a real thing.

simphys
Orodruin said:
That was not the point or the important part of my post. The important point came after.
Yeah, it just bothered me that it seems like you have to have some knowledge of the center of rotation to properly solve the equation.

erobz said:
I may have known that 15 years ago..."If you don't use it, you lose it" is a real thing.
A quick check up and you're good to go if you would ever need it

erobz
Orodruin said:
Luckily Einstein’s theory showed that free falling objects have zero proper acceleration and he was saved as he adopted a local inertial feame where there was no ”up” for the apple to fall from.
The funny part of this (for me) was laughing at how hard I had to think...to not get it!

simphys
erobz said:
The funny part of this (for me) was laughing at how hard I had to think...to not get it!
Hahaha it happens sometimes. At least you get it now, I hope at least
xD

I mean if not it's whatever really.. you didn't these 15 years anyways lol

simphys said:
I mean if not it's whatever really.. you didn't these 15 years anyways lol
Yeah...you'd be surprised by what you can get away with, without knowing.

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