Section 2

Friction and Gravity

Friction

A Smooth Surface? If you look at the polished surface of an aluminum alloy under a powerful microscope, you’ll find that it is actually quite rough.

FrictionThe force that two surfaces exert on each other when they rub together

A Smooth Surface? If you look at the polished surface of an aluminum alloy under a powerful microscope, you’ll find that it is actually quite rough.

FrictionThe force that two surfaces exert on each other when they rub together

The strength of the force of friction depends on 2 things

how hard the surfaces push together

the types of surfaces involved

A Smooth Surface? If you look at the polished surface of an aluminum alloy under a powerful microscope, you’ll find that it is actually quite rough.

Types of Friction

Types of FrictionStatic Friction: Friction that acts on objects that are not moving

Types of FrictionStatic Friction: Friction that acts on objects that are not moving

Sliding Friction: Occurs when two solid surfaces slide over eachother

Types of FrictionStatic Friction: Friction that acts on objects that are not moving

Sliding Friction: Occurs when two solid surfaces slide over eachother

Rolling Friction: When object rolls across the surface

Types of FrictionStatic Friction: Friction that acts on objects that are not moving

Sliding Friction: Occurs when two solid surfaces slide over eachother

Rolling Friction: When object rolls across the surface

Fluid Friction: Water, oil, other liquids cause the object to move easily

Static FrictionTo make the sled move, the athlete firsthas to overcome the force of static friction.Static friction acts in theopposite direction to theintended motion.Sliding FrictionOnce the sled is moving, itslides over the floor. Slidingfriction acts between the sledand the floor in the oppositedirection to the sledʼs motion.Rolling FrictionRolling friction occurs whenan object rolls over a surface.For the skateboarder, rollingfriction acts in the directionopposite to the skateboardʼsmotion.Fluid FrictionWhen an object pushes fluidaside, friction occurs. The surfermust overcome the fluid frictionof the water.Static frictionIntended directionof motionSliding frictionDirection of motionFluid frictionDirection of motion Rolling friction

Gravity

GravityStudyJams

GravityStudyJams

Gravity is a force that pulls objects toward each other

GravityStudyJams

Gravity is a force that pulls objects toward each other

Newton realized that Gravity acts everywhere in the universe

GravityStudyJams

Gravity is a force that pulls objects toward each other

Newton realized that Gravity acts everywhere in the universe

The law of Universal gravitational states that the force of gravity acts between all objects in the universe

Gravity Continued

Gravity ContinuedTwo factors affect the gravitational attraction between objects:

Mass

Distance

Gravity ContinuedTwo factors affect the gravitational attraction between objects:

Mass

Distance

Force also depends on the distance between the objects

Gravity ContinuedTwo factors affect the gravitational attraction between objects:

Mass

Distance

Force also depends on the distance between the objects

Mass is the measure of amount of matter, not to be confused with weight

Gravity and Motion

Gravity and MotionFree Fall: When an object is accelerating while its falling

Gravity and MotionFree Fall: When an object is accelerating while its falling

Air Resistance:

Gravity and MotionFree Fall: When an object is accelerating while its falling

Air Resistance:

Terminal Velocity: is reached when the force of air resistance equals the weight of the object

Gravity and MotionFree Fall: When an object is accelerating while its falling

Air Resistance:

Terminal Velocity: is reached when the force of air resistance equals the weight of the object

Projectile Motion: Something thrown horizontally