Forces Friction & Gravity Chapter 2 Section 3

Friction The force that resists motion Smooth or rough? How hard are the objects pushed together?

Friction Good Things –Gives shoes traction –Let’s you strike a match Bad Things –Slows your bike down –Makes cars less efficient

Sliding Friction 1 object slides over another –Skiing

Rolling Friction 1 object rolls over another object –Train tracks

Fluid Friction Objects move through a fluid –“A well oiled machine” Better than sliding

Gravity The force that pulls objects to earth

Free Fall Maximum acceleration –No air resistance

Terminal Velocity F gravity = F air resistance Maximum falling speed

Air Resistance Fluid Friction –Objects moving through air

Projectile Motion When an object is thrown horizontally –Forms a parabola

Weight Force of gravity on your body –Earth Gravity = 9.8 m/s 2 –Moon Gravity = 1.6 m/s 2 1/6 on the moon –Mr. Cady = 28 lbs.

Law of Universal Gravitation All objects in the universe are attracted to one another Stronger when… –Bigger –Closer