2. Two main causes Friction Friction Two solid objects sliding against each other. Two solid objects sliding against each other. Drag Drag The backwards drag of a solid object moving forward through a fluid. The backwards drag of a solid object moving forward through a fluid.

3. Cause of Friction The hills and valleys of 2 objects acting upon each other. The hills and valleys of 2 objects acting upon each other.

4. Causes Cont. Friction varies with the weight, normal force, pull, and force of friction on an object. Friction varies with the weight, normal force, pull, and force of friction on an object. Objects are considered to be in equilibrium if the weight and normal force are = in size and opposite in directions. Objects are considered to be in equilibrium if the weight and normal force are = in size and opposite in directions.

5. Forces acting on an object

6. Ways of Reducing Friction Wet Friction Wet Friction Adding lubricants to reduce the frictional forces between parts. Examples Rolling Friction Rolling Friction Adding rolling parts to an object to reduce frictional forces between parts. Examples wheels, ball bearings, etc. Oil, grease, water, etc.

7. How lubricants work Separates surfaces Separates surfaces Places friction on lubricant Places friction on lubricant Picture here

8. How rolling friction works Surfaces don’t scrape together as much Surfaces don’t scrape together as much Frictional Force is always less than sliding friction. Frictional Force is always less than sliding friction. Picture here

9. 2 Modes of Friction Static Initial force used to start moving an object. Kinetic Kinetic Force used to keep an object in motion Static > Kinetic

10. Drag Produced by a fluid moving over a solid object. Produced by a fluid moving over a solid object. – Fluids can be a liquid or a gas – Acts just like a lubricant in its movement – Causes turbulence on the solid object – Increases in a linear pattern to a point picturepicture

11. Ways of Reducing Drag Streamlining Streamlining – Creating a more aerodynamic solid object to reduce turbulence picturepicture