Transcript Regents Physics - Forestville Central School / Overview

Regents Physics
Projectile Motion
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
Projectile Motion
Click on the pictures for animations
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Bullet Demonstration
Ballistics Cart Demo
Important Concepts
1. Vertical and horizontal motions are independent of each other
2. 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)
3. We use basic motion equations to solve!
What do You Notice??
This is Splat the Cat
R.I.P
Splat the Cat’s days are numbered….Why??
Projectiles Launched Horizontally
Splat the cat is tossed horizontally at 20 m/s
off a cliff that is 50 m high.
a) How long is the Splat in the air?
b) How far from the base of the cliff
does Splat land?
c) How fast is the cat moving the
Instant before he Splats?
Problems Solving Strategy
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1. Write known and unknown variables
2. Write variables for x and y directions
What’s missing?
vyf = ?
yi = 0
vyi = 0
vxi = 20 m/s
ay = g = -9.8m/s2
ax = 0
WHY?
vxf = 20 m/s
vnetf = ?
yf = -50 m
xi = 0
t=?
xf = ?
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
Projectiles at Any Angle..a few differences
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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 … we’ve
done this before!
Vxi = Vocos 
Vyi = Vosin 
Variables of Motion
Click
Demos
Distance
 Firing angles
 How is time affected?
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2nd demo
Other differences and similarities
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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!
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
Let’s Play Golf
Click