________________ - the force resisting the relative motion of solid surfaces sliding against each other
What are factors that affect friction?
We often think that friction stops us from moving. What are examples where friction is necessary for movement?
What causes friction?
There are two types of friction: _________________ (moving) and ________________ (stationary).
Coefficient of friction
· a dimensionless scalar value greater than zero
· describes the ratio of the force of friction between two bodies and the force pressing them together
· Represented by
· A property of the material the surfaces are made of
Kinetic Friction :
While an object slides over another object, we assume the force of friction does not depend on the speed of the object.
· is the coefficient of kinetic friction.
· FN is the normal force between the two objects.
Static Friction :
Static friction is the friction that opposes the start of motion. The size of the friction force exactly balances the force of the push until a maximum is reached. The maximum value of the force (before the object starts to slide) is given by:
· = coefficient of static friction
· Is slightly ____________ than
Wood on dry snow
Example 1 A block is pushed along the floor with a force of . If , What is its acceleration?
Example 2 The same block is now resting on the floor where . What force is required to make the block move?
Example 3 A block of wood sits on a wooden floor. The largest horizontal force that can be applied to the block before it will start moving is . Once the block starts moving, it only takes to keep moving at a constant velocity.
a) Calculate the coefficient of static friction for the block and the floor.
b) Determine the force of friction acting on the block if a horizontal force of [E] acts on the block.
c) Determine the coefficient of Kinetic friction.
Example 4 A car of mass is driving at when the car hits a patch of ice. The driver...