1. FRICTION!

2. Friction – force that opposes (slows) motion
Vector Quantity
Types of Friction – Rolling, Sliding and Fluid
Frictional Force Depends on –
Normal Force of object (Weight)
Type of surface

3. Static Friction – Opposes the START of motion (when object is at rest)
Kinetic Friction – Objects in contact that are moving past each other.
Kinetic Friction < Static Friction

4. Frictional forces are PARALLEL to surfaces
In order to get an object moving or keep it moving, it must overcome the frictional force.
Fapplied = 14.8 N
Ffs = 14.8 N
20 N Steel Box

5. **If Frictional Force = Applied Force
then the object is at rest or moving at constant velocity**
**If Applied Force > Frictional Force
then the object is accelerating in the direction of the applied force.**

6. Force of Friction

7. Problem
A force of 10 Newtons towards the right is exerted on a wooden crate initially moving to the right on a horizontal wooden floor. The crate weighs 25 Newton’s.
Calculate the magnitude of the force of friction between the crate and the floor.
What is the net force acting on the crate?
Is the crate accelerating?