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22 vectors projectile motion

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									        Physics LG
      Jan. 30, 2009




   Vectors &
Projectile Motion
 Motion is Relative



► Frameof Reference - perspective from
 which you observe
           Truck at Rest




If the ball is thrown at 60 km/h relative to
the truck, at what velocity will the person
               catch the ball at?
           Truck Moving Away




► If the ball is thrown at 60 km/h west relative to
  the truck and the truck moves at 40 km/h east
  relative to the catcher, at what velocity will the
  person catch the ball at?
         Truck Moves Towards




► Ifthe ball is thrown at 60 km/h west relative to
  the truck and the truck moves at 40 km/h west
  relative to the catcher, at what velocity will the
  person catch the ball at?
► Scalar   - measurement of magnitude only
   Ex) mass, volume, speed


► Vector   - measurements with both
 magnitude and direction
   Ex) velocity, acceleration, force
            Vectors


        arrowhead = direction

length of arrow = magnitude
Vector addition
Resultant – sum of vectors
Pythagorean Theorem
    a2 + b2 = c2
► c2 = a2 + b2
► c2 = 802 + 602
► c2 = 6400 + 3600
► √c2 = √10,000
► c = 100 km/hr
Example Problem

          ► c2 = a2 + b2
          ► c2 = 42 + 32
          ► c2 = 16 + 9
          ► c2 = 25
          ► c = 5 km/h
        Vector addition
►   Pythagorean Theorem -

►   Parallelograms -

►   Head-to-tail method -


►   Trigonometry -
   Vector Addition
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=51
 What is the vertical and horizontal
     component of a vector?
http://www.batesville.k12.in.us/Physics/APPhyNet/Vectors/Hor_&_Vert_Comps.html
           Projectile Motion
Projectile – an object moving through air
 affected by gravity
             Projectile Demos
► Shooter/Dropper
► Monkey and Hunter
            Projectile Motion
Horizontal and vertical motion act independently

                               1 2
        d x  vt          d y  at
                               2
How fast is the ball thrown?
► Vertical             ► Horizontal

► d= .5at2             ► v= d/t
► 5 = .5(10)t2         ► v= 20m/1s

► t= 1 second          ► v= 20 m/s


         The ball is thrown at 20 m/s!
Upwardly-Moving Projectiles

                  What angle should
                  a ball be kicked to
                   get the farthest?
Projectiles launched at the same
   speed but different angles.
Shot Put - 45º is not the ideal angle, why?

You are already off the ground 1-2 meters.
45º is the ideal angle for high speed
        projectiles either. Why?

Air resistance must be considered.
         Fast Moving Projectiles
► What would happen if you threw a ball so fast that
 the curvature of the earth came into play?
         Fast Moving Projectiles
           a projectile traveling fast enough to fall
► Satellite-
  around the earth rather than into




► To  stay in orbit around the earth, a satellite needs
  to travel at 8 km/s!
Hang Time
Due Next Week
   POTW
   11s Bull’s eye lab
   12s Rocket Lab
   30s Motion Worksheet #1
   31s Motion Worksheet #2
   32s Motion Review
   Test will be next Thursday Feb 5th
     ►Study the 1s, 2s, labs, and worksheets
     ►Use the back page of booklet under
      motion for note sheet for test.

								
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