Docstoc

Physical Science

Document Sample
Physical Science Powered By Docstoc
					Chapter 11 - Forces
      Section 1
Laws of Motion
         p. 346
I. Newton’s First Law - Inertia

 A. Inertia- tendency for an object in
    motion to stay in motion and an object
    at rest to stay at rest unless acted
    upon by an outside force
 B. Heavier objects have more inertia
  Chapter 11   Section 1 Laws of Motion



Newton’s First Law
  Chapter 11   Section 1 Laws of Motion



Mass and Inertia
II. Newton’s Second Law

A. Force is equal to mass times acceleration
               F=ma

B. Measured in Newtons
        1 Newton = 1 kg x 1 m/s2 = 1 N
  Chapter 11   Section 1 Laws of Motion



Newton’s Second Law
Force Diagrams
 Force diagram – diagram showing all forces acting on
 an object
Drawing a force diagram
1. Identify object you will draw a diagram for
2. Draw a dot to represent the object
3. Identify forces acting on the object (they
   will be in direct contact)
4. Draw a vector to represent each force
  a) In the direction of the force
  b) Proportional to its magnitude
Section 2
  Gravity
   p. 352
  Chapter 11   Section 2 Gravity



Law of Universal Gravitation
I. Universal Gravitation Equation
          F= G(m1m2/d2)
     A. All matter is affected by & exerts
       gravity
     B. Gravity increases as mass increases
     C. Gravity decreases as distance
       increases
II.     Free Fall and Weight
      A. Free fall- when gravity is the only
          force acting on an object
           hammer and feather on the moon


      B.      Gravitational acceleration constant
              on Earth is 9.8 m/s2 = g
C.     Weight equals mass times free fall
       acceleration (gravity)
     1. w=mg
     2. In space, you seem weightless
         because everything is
         accelerating (falling) at the same
         rate
D. Weight and mass are different.
  1. Mass is the same wherever you are
  2. Weight varies according to gravity
     Ex: moon = g = 1.6 m/s2



    mass vs weight
E. Terminal Velocity – an object is no longer
   accelerating because gravity is balanced
   by air resistance
  1)   when something is falling, you can calculate
       the distance it fell using the formula d= ½ gt2
F. Orbital Motion – a combination of free
   fall caused by gravity and forward
   motion maintained by inertia
III. Projectile Motion – the curved path of an
     object due to combination of 2 forces
    A. forward motion creates horizontal
       aspect
    B. Gravity creates vertical aspect
Projectile Motion
          Section 3
Newton’s Third Law
             p. 360
I. Action and Reaction
    A. For every action [force], there is an
     equal and opposite reaction [force]
         1. forces are in pairs – equal in
         size but opposite in direction
         2. force pairs do not act on the
         same object so each object’s
         motion is different
         3. Equal force does not always
         have equal effects
  Chapter 11   Section 3 Newton’s Third Law



Action and Reaction Forces
II. Momentum
     A. Momentum (p=mv) mass x velocity
             p= kg x m/s (+ direction)
       1. Force is related to change in
          momentum over time
       2. Momentum is conserved in
          collisions
       3. Can be transferred between
          objects
         a. Any momentum that is not
            transferred in a collision is
            conserved
B. Law of conservation of momentum
   - the total amount of momentum in
   an isolated system is conserved
Momentum and Collisions
Summary of Newton’s laws
Law of universal gravitation: all
 objects have gravity, more mass =
 more gravity; more distance = less
 pull from gravity
1st law of motion: inertia
2nd law of motion: f=ma
3rd law action/reaction

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:5
posted:4/10/2011
language:English
pages:26