Maintaining contact in vertical circular motion

[appianway]

I know that contact is maintained so long as N > 0, but would anyone care to give a more detailed description?

[naved_s9994]

v^2 = gr

the minimum speed to pass through the top

[appianway]

I know...

I was hoping that someone would give me a detailed description about why this occurs...

[naved_s9994]

ohh.. lol, MAO MAO MAO ..hehhe

[appianway]

LOL it's weird because I understand how it works (a>g for contact to remain), but I can't put it into words well...

[IntoTheNewWorld]

I'm just thinking that without a normal reaction force, the thingy in question is just hanging in the air, if there is contact the roller coaster track or whatever must be giving it a normal reaction force.

[Mao]

It's related to the normal reaction force, which can only act in the direction AGAINST the surface (assuming it's a simple smooth surface, not velcro)

For inside loop (at the top), (they act int the same direction), however, when the required centripetal acceleration is LESS than g [that is, ], it implies N must be negative. This is impossible as N can only act downwards. Hence the object is not in contact with the surface. The minimum velocity is

For outside loop (at the top), (mg acts downwards, N acts upwards). However, when centripetal acceleration is GREATER than g [that is, ], it implies N must be negative. This is impossible as N can only act upwards, Hence the object is not in contact with the surface (it launches off the surface like in racing games). The maximum velocity to maintain contact with the surface is

[Mao]

I'm just thinking that without a normal reaction force, the thingy in question is just hanging in the air, if there is contact the roller coaster track or whatever must be giving it a normal reaction force.

That is not necessarily true. The normal reaction force can be zero, it is still in contact with the surface but the surface does not exert a force on it.

The thing is the normal reaction force must NOT be negative (i.e. pointing towards the surface).