Friction

Page
1

Slide 1

Types of Friction

Force of Kinetic Friction

This value represents the relative force necessary to keep an object moving at a constant rate

Force of Static Friction

This value represents the relative force necessary to make an object move

Slide 2

Frictional Force Resisting Motion

Force Causing the Object to Move

Kinetic Region

Static Region

Max

Slide 3

Frictional Forces Occur When Materials are in Contact

W

fs

F

N

Surfaces in Contact

M1

Spring Scale

F = Force Causing Motion (Pull on Scale)

Fs = Force of Static Friction (Resists Motion)

N = Force Normal Holds Surfaces in Contact

W = Weight of Object ( Mass x Gravity)

Slide 4

Friction is a Force That Resists Motion

W

fs

F

N

Surfaces in Contact

The Pink Block M1 Will not Move Until the Force F (Pull on the scale ) Exceeds the Force of Static Friction fs.

M1

Spring Scale

Slide 5

The Relative Force of Static Friction Between 2 Objects is Expressed as the Quotient of the Force (F) Required to Move the Object

W

fs

F

N

Surfaces in Contact

M1

Spring Scale

Divided by the Weight W of the Object

This is Called the Coefficient of Friction

Slide 6

W

fs

F

N

Surfaces in Contact

M1

Spring Scale

= Force Required to Cause Motion

= Weight of Object

= Coefficient of Friction

Coefficient of Static Friction

Slide 7

Using the Gears-IDS Battery to Calculate The Static

Coefficient of Friction

Slide 8

Record the Maximum Force (F) (Before the Battery Begins to Move)

Maximum Force F = 110 g

Slide 9

Record the Weight (W ) of the Battery

580 g

Slide 10

The Coefficient of Static Friction Between the Wood Desktop and the Plastic Battery is Described Algebraically:

= 580 g

= 110 g

= .190

Slide 11

The Coefficient of Kinetic Friction Can be Found Using the Same Technique