Chapter 2--THE DAWN OF MODERN SCIENCE

Solutions to Numerical Exercises

Key Concepts:

  • Velocity--includes a direction
  • Acceleration--change in velocity
  • Force--also know what Net Force means
  • Mass--inherent property of an object
  • Weight--realize that this is a force
  • "Dawn of Modern Science"--math & experiements

    Newtons Laws: (you must translate)
    1) F=0 -> a=0 -> v=constant
    2) F=ma
    3) Force(me-push-you) = Force(you-push-me)

    Pretty much all forms of transportation utilize the 3rd law. Think about it!



    • Motion in a plane --two cases 
    Uniform Acceleration
	There is a net force, which means there is acceleration.
		v = a t		d=1/2 a t^2
 

Constant Motion
	The net force is zero, which means the acceleration is zero.
		v = constant	d= v t

EX: Projectile Problem--seperate horizontal from Vertical 
	Vertical:  Force of gravity -> a = 9.8m/s^2  UNIFORM ACCELERATION

	Horizontal:  No Force  -> a=0    CONSTANT MOTION  

Remember that the time of flight is the only way that the horizontal and vertical motions are
related to each other, and this time is usually found by looking at the vertical equations.
Why?

    Motion in a circle 
    	There is a force constantly changing the direction of the thing
	  so that goes in a circle.  This means that there is an acceleration inward.
			a= v^2/r      v= 2 pi r / T
			"r"   is the radius of the circular motion.
			"T"  is the period of the motion  (the time it takes to go around once)

    Demos: 

    
Ball rolling down track (ala Galileo)-- Showed that nature can be described
		with simple mathematics.    
		Result:   d~t  or  d~t^2?  

Drop & Throw a piece of chalk at the same time-- Showed that 
		vertical and horizontal motion are independent.  
		How did it do that?
		Result: Which landed first?
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