Friction

What is friction?

Friction is a force, affects motion. Friction acts on materials in contact with another, or acts in different direction in opposite motion.

What does the force of friction depend on?

• Nature of the materials.
• How hard the surfaces are pressed together

..such as Rubber vs. Concrete, and not Steel vs. Steel (Rubber vs. Concrete > Steel vs. Steel)

Static Friction :

Friction between the surfaces in contact and which are relatively at rest.

• Opposes movement of stationary object
• Moving furniture
• Hardest part getting moving

Kinetic Friction

• Acts on objects in motion
• Once object begins moving, less force to keep in motion
• Sliding, Rolling, Fluid

Sliding Friction

Basketball shoes prevent slipping, relation to Sliding Friction

• Two objects slide past one another
• Basketball shoes prevent slipping

Rolling Friction

• Objects such as wheel or ball rolls across surface
• Easier to overcome than sliding friction
• Rolling friction is always less than static friction, as the time period for contact of irregularities between the bodies is less in rolling friction compared to static friction.

Fluid Friction

Boy with a helmet, on training wheels, relation to Fluid Friction

• Solid objects move through fluids
• Cyclists use aerodynamic and spandex to reduce friction
• Vehicles such as aeroplanes and cars have a special shape known as streamlined shape to reduce windshear or drag.

Air Resistance

• Friction acting on something moving through air
• Don't notice unless at high speed.

quiz

1 What is ________? It is a force that affects motion and acts on materials in contact with another, or acts in a different direction in opposite motion.

	friction
	gravity
	inertia
	tension

2 What does the force of friction depend on? It depends on the ________ of the materials and how hard the surfaces are ________ together.

	nature | pressed
	weight | pulled
	volume | pushed
	density | separated

3 Which type of friction opposes the movement of a stationary object and is evident when moving furniture?

	static friction
	kinetic friction
	rolling friction
	fluid friction

4 Which type of friction is related to basketball shoes preventing slipping?

	sliding friction
	rolling friction
	fluid friction
	static friction

5 Which type of friction is always less than static friction due to the short time period for contact of irregularities between the bodies?

	rolling friction
	sliding friction
	fluid friction
	kinetic friction

6 Which type of friction is related to a boy with a helmet on training wheels and cyclists using aerodynamic gear and spandex?

	fluid friction
	rolling friction
	sliding friction
	static friction

7 What is the friction called that acts on something moving through air, especially noticeable at high speeds?

	air resistance
	fluid friction
	sliding friction
	static friction