Newtons Second Law EF= ma

[Mao]

Inside loop:

Top: F net = N + mg (points towards the same direction)

Bottom: F net = N - mg (points upwards, N > mg)

Outside loop:

Top: F net = mg - N (points downwards)

ye i meant when its outside the loop

Interesting thing about circular motion in the vertical direction outside of the loop:

At top:
gravitational attraction downwards
normal reaction force by surface on object upwards

Net force = mg - N = Fc, points downwards towards center of circle

At bottom:
gravitational attraction downwards
normal reaction force by surface on object downwards

Net force = mg + N, points downwards AWAY from center of circle :. circular motion not possible.

[dino]

AWAY? I'm lost now. grrr. i need more vertical questions.

[img]http://img.skitch.com/20090607-cywdej8pyjf85yey5e3pre35uw.preview.jpg[/img]

is that wrong?

[TrueTears]

AWAY? I'm lost now. grrr. i need more vertical questions.

[img]http://img.skitch.com/20090607-cywdej8pyjf85yey5e3pre35uw.preview.jpg[/img]

is that wrong?

That is correct.

[dejan91]

Are these forces with or without a direction??

So is:

Top: F net = N + mg, N subtract mg (because opposite direction).

 F net = N - mg, N subtract the negative of mg. (i.e. adding mg to N)

Outside loop:

Top: F net = mg - N,..............(i don't even know what way to explain this lol)

I just tend to use intuition for these really......... but can anybody explain this?

[TrueTears]

Are these forces with or without a direction??

So is:

Top: F net = N + mg, N subtract mg (because opposite direction).

 F net = N - mg, N subtract the negative of mg. (i.e. adding mg to N)

Outside loop:

Top: F net = mg - N,..............(i don't even know what way to explain this lol)

I just tend to use intuition for these really......... but can anybody explain this?

When you are on the top:

Let up be negative and down be positive.

Since forces are vectors, they are all pointing down hence they are all positive: We have

When you are on the bottom.

Let up be positive and down be negative.

Normal force is acting up, is acting up, mg is acting down:

[dejan91]

Ahhhh ok so you use those "formulas" with the absolute value of N and mg, correct?

[TrueTears]

Ahhhh ok so you use those "formulas" with the absolute value of N and mg, correct?

Yeap, then just put the +/- sign depending on the direction.

So if you are on the bottom: (lol...)

[dejan91]

Lolll, I take it you mean depending on where you are in the circle? (lets not confuse direction with position now haha)

But yes, I get it now.

[naved_s9994]

lol kurry muncher, what the heck...anyways.. !!

umm, yea thanks everyone...CLEARED it all up

[NE2000]

Inside loop:

Top: F net = N + mg (points towards the same direction)

Bottom: F net = N - mg (points upwards, N > mg)

Outside loop:

Top: F net = mg - N (points downwards)

ye i meant when its outside the loop

Interesting thing about circular motion in the vertical direction outside of the loop:

At top:
gravitational attraction downwards
normal reaction force by surface on object upwards

Net force = mg - N = Fc, points downwards towards center of circle

At bottom:
gravitational attraction downwards
normal reaction force by surface on object downwards

Net force = mg + N, points downwards AWAY from center of circle :. circular motion not possible.

So is that if you are outside of the circle when at the bottom, so you are upside down and there is no possibility of a centripetal force?

[kamil9876]

Inside loop:

Top: F net = N + mg (points towards the same direction)

Bottom: F net = N - mg (points upwards, N > mg)

Outside loop:

Top: F net = mg - N (points downwards)

ye i meant when its outside the loop

Interesting thing about circular motion in the vertical direction outside of the loop:

At top:
gravitational attraction downwards
normal reaction force by surface on object upwards

Net force = mg - N = Fc, points downwards towards center of circle

At bottom:
gravitational attraction downwards
normal reaction force by surface on object downwards

Net force = mg + N, points downwards AWAY from center of circle :. circular motion not possible.

So is that if you are outside of the circle when at the bottom, so you are upside down and there is no possibility of a centripetal force?

Well, If the car was a N magnet and you placed some S magnet in the centre, or place some really large planet above the hoop, or maybe have a favourable ammount of upward wind on that day then maybe you could . But if the the only two forces are the Normal Reaction force of hoop and gravity of earth and car then no because they always act down in this situation and the centre is above you so obviously a centripetal force would have to be upwards.