Friction and gravity

  • #1

Main Question or Discussion Point

The formula of friction force is

Ff = μN

can also be defined as

Ff = μ.m.g

One of my friend say that mathematically, that equation tell us that when there is a gravity force, Ff can't be zero assuming that there is no zero μ

Is that true? While on static condition I will say that even when there's a gravity force, the friction force is zero. But he said then if it is in static condition, then the formula would be

Fmax = μ.m.g

which mean when there is a gravity force, Fmax can't be zero.

Can physics really defined just by formula mathematically?
 

Answers and Replies

  • #2
tiny-tim
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The formula of friction force is

Ff = μN
No, that only applies to dynamic friction and when the bodies are about to become dynamic (ie Fstatic = Fmax).

In the static case, Ff < µN
… But he said then if it is in static condition, then the formula would be

Fmax = μ.m.g

which mean when there is a gravity force, Fmax can't be zero.
Yes, Fmax can't be zero, but Ff can be zero.
 
  • #3
Yes, Fmax can't be zero, but Ff can be zero.
Is that true that the only condition Ff can be zero on gravity influence, is when the mass become completely static?
 
  • #4
tiny-tim
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I don't really understand what you're asking. :confused:

If the mass is moving, then the friction force is always µN.
 
  • #5
10
0
Which us easier to pull or push?Is there any impact of friction?If so how the mass will effect to that?
 

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