Types of Friction What is Friction Friction is

Types of Friction

What is Friction? �Friction is the resistance to the sliding, rolling, or flowing motion of an object due to its contact with another object. �When a moving object comes in contact with another object, friction is the opposing force that slows or stops the moving object.

�Without friction, an object would continue to move at constant speed forever. �The strength of the force of friction depends on the type of surfaces and how hard the surfaces push together. �Rough surfaces produce greater friction than smooth surfaces.

�Without friction you could not Write Drive a car Fly an airplane �Why not?

Four Types of Friction �Rolling Friction �Static �Sliding Friction �Fluid Friction

What do all these things have in common?

Rolling Friction �Rolling friction is friction that occurs between surfaces in motion in which one of the surfaces is a wheel, roller, or ball. �Examples: Riding a bike – tires and ground Bowling – ball and lane

What do all these things have in common?

Static Friction �Static friction is friction that occurs when the surfaces in contact are at rest (not in motion). �Examples: A book resting on a desk. A potted plant sitting on a sidewalk.

What do all these objects have in common?

Sliding Friction �Sliding friction is friction that occurs when solid surfaces slide over one another. �Examples: Writing – pencil point and paper Combing your hair – surface of comb and strands of hair

What do all these things have in common?

Fluid Friction �The force that tries to slow objects down when they move through a liquid or a gas. It's also known as "drag", or "air resistance". �All gases and liquids are fluids. �An airplane and a swimmer both experience fluid friction.

Ways to Reduce Friction �Smooth the surface �Replace rolling with sliding �Add oil or another type of lubricant

Friction Song �What is friction? Friction Video

Gravity and Free Fall �An object is in free fall when the only force acting on the object is gravity. �Free-falling objects do not encounter air resistance. �In free fall, the force of gravity is an unbalanced force.

Calculating Free Fall All objects in free fall accelerate at the same rate – 9. 8 m/s² - regardless of their mass. in one second = 9. 8 m/s² in two seconds = 19. 6 m/s² in three seconds = 29. 4 m/s² in four seconds = ____ The velocity continues to increase as the object falls.

Gravity, Free Fall, and Projectile Motion �An object that is thrown is called a projectile. �If there is no air resistance, an object that is dropped and an object that is thrown are both in free fall. �Without the force of air resistance, both objects will hit the ground at the same time.

Gravity and Air Resistance �Most objects falling through air experience a type of fluid friction called air resistance. �Air resistance is not the same for all objects. �The greater the surface area of the object the greater the air resistance. �However, since the elephant has more mass, it has more downward force of gravity and falls faster.

What type of friction?

�Static Friction

What type of friction?

�Rolling Friction

What type of friction?

�Fluid Friction

What type of friction?

�Static Friction

What type of friction?

�Sliding Friction

What type of friction?

�Fluid Friction