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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

length of arrow = magnitude
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
►   Pythagorean Theorem -

►   Parallelograms -

►   Trigonometry -
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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