What happens if the normal reaction force is less than zero?

[goldfish9776]

Homework Statement

why the object will fall of when the normal reaction force is less than zero ? P/s : the normal reaction force is in downward direction...
How if if the normal reaction force is less than zero ? the normal reaction is in upward direction ?

Homework Equations

The Attempt at a Solution

 

[andrevdh]

The track can only push the object away, not pull it towards it.

 

[goldfish9776]

The track can only push the object away, not pull it towards it.

I still don't understand why when the normal reaction force is less than zero , the object will lose contact with the track ?

 

[andrevdh]

N is the normal reaction force from the track.
If the object is not pushing against the track
then it lost contact with it!
Which means it is falling.
So if N is upwards, or negative, which is impossible
since it cannot pull the object towards it, then the object
is falling. In the limiting case where it as the ppoint of leaving the
track N = 0. At this point it is "floating" and wants to leave the track
or at the point of falling since the only force on it is gravity or its weight.

 

[goldfish9776]

N is the normal reaction force from the track.
If the object is not pushing against the track
then it lost contact with it!
Which means it is falling.
So if N is upwards, or negative, which is impossible
since it cannot pull the object towards it, then the object
is falling. In the limiting case where it as the ppoint of leaving the
track N = 0. At this point it is "floating" and wants to leave the track
or at the point of falling since the only force on it is gravity or its weight.

If the object is pushing against the track ,the object will surely losing contact with the track right , the object would fall of ?

 

[andrevdh]

No, if the object is pushing against the track then it means it is supported by the track.
Just like if you stand on the floor you push against it and it supports you with the normal force.

 

[goldfish9776]

No, if the object is pushing against the track then it means it is supported by the track.
Just like if you stand on the floor you push against it and it supports you with the normal force.

Ok, I think I can understand it...

 

[Aayat]

Ok, I think I can understand it...

i am able to understand it ...why N is less than zero

 

[haruspex]

i am able to understand it ...why N is less than zero

Is that what you meant to post, that you do understand? If so, that's nice, but why are you telling us?