# Normal force

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##### Full Member
5+ Year Member

I know this is kind of a stupid question but could anyone give me a clear cut definition of the normal force?

I know the basics about it, usually is mg on linear surfaces, how its related to friction, but I get confused about what exactly it equates to when it gets into objects with multiple forces on rotating objects and such.

Thanks

#### TheBoondocks

##### StreetFighter 4 Virtuoso
15+ Year Member
I know this is kind of a stupid question but could anyone give me a clear cut definition of the normal force?

I know the basics about it, usually is mg on linear surfaces, how its related to friction, but I get confused about what exactly it equates to when it gets into objects with multiple forces on rotating objects and such.

Thanks

Force normal is a force perpendicular to the surface of an object. It is related to friction because the Force normal acts to NORMALLY balance gravity or the component of gravity opposite to it. For an object to remain ground the vertical components must balance even if it's accelerating like down an incline or on level ground. Since in many cases it is a function of mg, that's why Fs=Fn*us or substitute Fk if needed.

In circular motion at the top, Force normal and Gravity are in the same direction towards the inside of the circle so Fn+mg=(mv^2)/g