2.  1. Galileo wrote this:  Objects naturally tend to go in straight lines at constant speed. ◦ He IMAGINED no friction/air resistance ◦ He knew air resistance actually depended on speed. ◦ Late 16 th Century  Newton: Objects maintain constant velocity,  UNLESS  http://www.scitechantiques.com/cycloidhtml/ http://www.scitechantiques.com/cycloidhtml/  http://www.youtube.com/watch?v=5C5_dOEyAfk http://www.youtube.com/watch?v=5C5_dOEyAfk 2

3.  Unless something makes them CHANGE.   F= “Net Force” (N)  M mass (kg)  =change in motion  (Newton Called it)acceleration!! a (m/s 2 ) 3

4.  Causes of Change (Net Force) = a (Motion Change)  Resistance to Change (Inertia/mass)   F α a Given constant mass, Acceleration is proportional to the Net Force  (1/m) α a Given a constant net force, the acceleration is inversely proportional to the mass. 4

5.   is the Greek letter “S”. It means “sum” or “add up”.  Force- A push or a pull. Touching is not required. (Like magnets.) VECTOR  So  F is a sum of all forces acting on an object.  So what types of pushes and pulls do we have? 5

6.  Force of Gravity (near an object)  (Fundamental Force=Gravity) ◦ F g =mg ◦ g= 9.8 m/s^2 on Earth, 1.6 on Moon, 25 on Jupiter ◦ M= mass in kilograms 2.2lbs.=1kg. ◦ Acts straight down toward object.  Normal Force (Latin for 90 degrees)  (Fundamental Force=Electromagnetic) ◦ F N = That depends. ◦ It’s from electrons repelling electrons ◦ It’s a “contact” force. ◦ 90 degrees to the surfaces ◦ Always found via  F=ma. ◦ When 0 Normal Force, things aren’t “in contact”. 6

7.  Friction  (Fundamental Force=Electromagnetic) ◦ F=  F N OR f=  N ◦ Acts to RETARD motion (opposite your direction of motion) ◦ Parallel to a Surface ◦ Think of it as a translation from Normal Force to Sideways Force ◦ Two types  Static- An object is not moving, yet forces act.  Kinetic- once the object is “slipping”, “skidding”, “sliding”.  Static is usually greater than kinetic.  “Mu” is the coefficient of friction. ◦ s ◦ k ◦ Depends on BOTH surfaces touching. 7

8.  F.O.R.  F.B.D.  Force Table (x and y)  F=ma (x and y)  Finish the Formula 8

9. b  Forces come in pairs.  Forces are fundamentally an interaction between 2 objects!  F a,b =-F b,a 9 a

10.  http://www.youtube.com/watch?v=UJiC7U3J3 Jk http://www.youtube.com/watch?v=UJiC7U3J3 Jk  Something is conserved  What could that be?  http://www.physicsclassroom.com/class/mo mentum/u4l2b.cfm http://www.physicsclassroom.com/class/mo mentum/u4l2b.cfm 10