# Static Friction and mass

How does mass effect static friction??

Does it increase of decrease static friction

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Think of it this way...Is it easier to move a 1kg box or a 100kg box starting from rest? Of course, the 100kg box would need a lot more force because the normal force that the surface (assuming perfectly horizontal) exerts on the box is greater for the 100kg box than for the 1kg box. Thus it will be harder for you to move a 100kg box than a 1kg box. So , as mass increases, the static friction also increases

HallsofIvy
Homework Helper
I'm going to start of by asserting that mass DOESN'T affect static friction. If you had a small mass and a large mass sitting on a surface in a weightless situation, neither would have any static friction.

Weight affects friction (more correctly the force perpendicular to the surface). If you have a mass sitting on a horizontal plane, then its weight will be proportional to its mass so the static friction will be proportional to its mass.

On the other hand, if you have a small mass sitting next to a large mass on a horizontal plane, and you press really hard on the small mass, you will have increased it downward force (weight?) possibly to the point where its static friction is greater than that of the greater mass without increasing its mass.

How would a running shoe company use information of static friction help make a shoe???

Originally posted by marshall4
How would a running shoe company use information of static friction help make a shoe???
Perhaps to determine how much "grip" the shoe needs on certain situations, or surfaces?

Mass has no effect on the coefficient of static friction...If we increase mass, it doesn't mean that we need more applied force to move the object.. It only depend upon the surface on which an object is moving.

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What if you have two balls of uniform density distribution on a ramp with one ball 8' in diameter and one ball 1" in diameter. The balls are both given the same force to start down the ramp. Will the larger ball with larger mass and hence increased weight slow more than the small ball? Resulting in traveling less distance?