Regents Physics

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Regents Physics

• Projectile Motion

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Projectile Motion

• A projectile can be anything that moves though
  the air after it has been given an initial
  thrust or input force
• Projectiles are only under one force as they move
  through the air GRAVITY!
• We ignore air resistance in most cases to simply
  the problems
• There are two general categories
• Projectiles launched horizontally
• Projectiles launched at an angle

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Projectile Motion
Click on the pictures for animations

• Bullet Demonstration
• Ballistics Cart Demo

• Important Concepts
• Vertical and horizontal motions are independent
  of each other
• We can relate the height, time in the air, and
  initial vertical velocity of the projectile by
  using its vertical motion, then determine the
  range (x-distance)
• We use basic motion equations to solve!

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What do You Notice??
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This is Splat the Cat
R.I.P
Splat the Cats days are numbered.Why??
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Projectiles Launched Horizontally

• Splat the cat is tossed horizontally at 20 m/s
• off a cliff that is 50 m high.
• How long is the Splat in the air?
• b) How far from the base of the cliff
• does Splat land?
• How fast is the cat moving the
• Instant before he Splats?

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Problems Solving Strategy

• 1. Write known and unknown variables
• 2. Write variables for x and y directions

Whats missing?
vyf ?
ay g -9.8m/s2
yi 0
vyi 0
ax 0
vxi 20 m/s
WHY?
vxf 20 m/s
vnetf ?
yf -50 m
t ?
xf ?
xi 0
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Practice Problem 2

• A plane that is moving 200 m/s drops a package.
  The package takes 15 seconds to reach the ground.
• A) What height was the package dropped from?
• B) How far did the plane travel from the time the
  package was released until the package hit the
  ground? Is this the same distance the package
  travels?
• C) How fast was the package moving when it hit
  the ground?

End
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Projectiles at Any Angle..a few differences

• When projectiles are launched at any angle, the
  initial velocity has both horizontal and vertical
  components
• This means that Vo must be used, not just Vxi
  weve done this before!

Vxi Vocos ?
Vyi Vosin ?
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Variables of Motion
Click
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Demos

• Distance
• Firing angles
• How is time affected? 2nd demo

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Other differences and similarities

• Time in air is called flight time and ½ of flight
  time occurs at ½ range
• So..it takes the same amount of time to go up as
  it does to fall down
• At ymax, Vyf 0m/s
• Still, only force acting on the is gravity
• Still, no acceleration in the x direction!

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Practice Problem
A football is thrown with an initial velocity of
5.5 m/s at an angle of 49? above the horizontal.
1. How long did it take the ball to return to
the launching height? 2. What was the
maximum height the ball attained? 3. What was its
range?
Vyf 0 m/s
Max height
range
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Lets Play Golf
Click