Question: How is the direction of friction calculated in snowboarding?

In summary, friction is a force that opposes slipping between two surfaces and is directed opposite to the velocity of the object. The formula for calculating friction force is Ff = µ*Fn, where µ is the coefficient of friction and Fn is the normal force. However, for static friction, the formula is Ff <= µ*Fn, and the magnitude of Fn is determined by other forces in the problem.
  • #1
Mash
7
0
Hey,

Im making a snowboarding game. I'm using Coulomb's equation for friction:

Ff = coef_of_fric * normal force

This gives me the size of the frictional force. But how is the direction calculated? Is it the opposite of the direction of the velocity of the snowboarder? Or is it the opposite direction of the force applied on the snowboarder, gravity in this case. I thought the latter would have been the correct answer. However, when a snowboarder is moving along a flat surface, the force due to gravity is canceled out by the normal. Though the snowboarder is still moving, so there is still some friction. I think I might be missing a force, or vector or something somewhere...

Can someone help me please?f
 
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  • #2
Friction opposes slipping between surfaces, in this case between the board and the snow. It will be directed opposite to the snowboard's velocity.
 
  • #3
Well the easy way(since its a game) would to multiply the velocity by a constant less than one.And when the velocity is really small just make it 0.
 
  • #4
Well, that would certainly be easier than modeling it correctly.
 
  • #5
Ff = µ*Fn

Be carefull when using that formula. µ*Fn is the maximum friction force, so a better formula is

Ff <= µ*Fn

where µ is coeff'o'friction and Fn is normal force. The magnitude of Fn is so that the resulting force is zero, i.e. constant velocity.
 
  • #6
Nesk said:
Ff = µ*Fn

Be carefull when using that formula. µ*Fn is the maximum friction force, so a better formula is

Ff <= µ*Fn

where µ is coeff'o'friction and Fn is normal force. The magnitude of Fn is so that the resulting force is zero, i.e. constant velocity.

The first is appropriate for kinetic or "sliding" friction. The µ here is the coefficient of kinetic-friction µk. The net force on the object need not be zero in this case.

The second is appropriate for static friction, where it is Ff (not Fn) that is the frictional force that is needed to yield a zero net force, up to that maximum of µ*Fn. The µ here is the coefficient of static-friction µs.

The magnitude of Fn is generally not determined by Ff... but by other forces in the problem. (Fn and Ff are perpendicular components ("the legs") of the total reaction force R.)
 

1. What is friction and what direction does it act in?

Friction is a force that opposes motion between two surfaces in contact. It acts in the opposite direction of the applied force, or the force that is causing the objects to move.

2. How does friction affect the motion of an object?

Friction can either slow down or stop the motion of an object. It can also cause an object to change direction or rotate.

3. Is there a difference in direction of friction for sliding and rolling objects?

Yes, the direction of friction is different for sliding and rolling objects. For sliding objects, friction acts in the opposite direction of the sliding motion. For rolling objects, friction acts in the direction opposite to the direction of rotation.

4. Can friction ever be in the same direction as the motion of an object?

No, friction always acts in the opposite direction of the motion of an object. If the motion of an object changes, the direction of friction will also change accordingly.

5. How can we reduce friction between two surfaces?

Friction can be reduced by using lubricants, such as oil or grease, to create a smooth surface between two objects. It can also be reduced by using materials with low coefficients of friction, such as plastic or Teflon.

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