"the most beautiful thing we can experience is the mysterious... it is the source of all true...
TRANSCRIPT
• "The most beautiful thingwe can experience is the mysterious... It is the source of all true artand all science."
• - Einstein
What is a force?
• any straight-line push or pull
Units of force
Newton (metric) (weight of 1 apple)
Friction
A force that opposes motion between two surfaces that are in
contact
The Source of Friction
• When surfaces are rough
• Even if surfaces are covered in microscopic hills.
Two types of Friction
• Kinetic: Kinetic means “moving”
Sliding
Rolling
Kinetic Friction
• Rolling Friction: slows down the motion of an object rolling on a surface". Rolling friction slows down the motion of a tire rolling along the pavement.
Kinetic Friction
• Sliding Friction: "the force that occurs when two objects slide against each other". An example of sliding friction is striking a match against a rough surface.
Kinetic Friction
• The force of sliding friction is greater than the force of rolling friction.
Static Friction
• the force that keeps an object that is not moving in its place". A vase on top of a table is an example of static friction.
Ways to reduce Friction
• Lubricants: motor oil, wax and grease.
Ways to increase Friction
• Make examples rougher
• Examples: sand scattered on icy roads.