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Unit 3.1 Projectile Motion
Teacher: Dr. Van Der Sluys
Objectives
• Two dimensional motion– Vertical– Horizontal
• Projectiles– Falling– Falling with an initial horizontal velocity
Falling Objects
• All objects close to the surface of theearth will fall due to gravity with anacceleration of -9.8 m/s2
• This acceleration only occurs in thevertical direction and is independentupon motion in the horizontal direction.
• The horizontal velocity of a fallingobject will remain constant.
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Falling Versus Projectiles
The Equations
d = Vit + 1/2at2
a = (Vf - Vi)/t
Vf2 = Vi
2 + 2 ad
Get organized: Create A Table
d =d =
t =t =
Vf =Vf =
Vi =Vi =
a = -9.8 m/s2a = 0 m/s2
VerticalHorizontal
Note: tvertical = thorizontal
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Strategy
• Insert any given and known/assumedinformation into the table.
• Solve for the variables that are notknown using the appropriate equations.
• Don’t confuse the variables in thevertical and horizontal
Problem
• If an object rolls off a table that is 0.75m tall with a horizontal velocity of +2.0m/s, how far from the base of the tablewill the object hit the floor?
The Effect of ChangingInitial Velocity
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Launching Projectiles at Angles
Problem
• If a projectile is launched at an angle of30° above the horizontal with muzzlevelocity of 200 m/s, what are thevertical and horizontal components ofthis vector?
Answer: X = 173 m/s; Y = 100 m/s
Problem
• If a projectile is launched at an angle of30° above the horizontal with a muzzlevelocity of 200 m/s, how long will theobject be in the air if it hits the groundat the same height at which it waslaunched?
Answer: 20.4 s
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Problem
• If a projectile is launched at an angle of30° above the horizontal with a muzzlevelocity of 200 m/s, how far will theobject travel horizontally if it lands atthe same height as it was launched?
Answer: 3.53 x 103 m
Projectile Problem Solving
1. Determine the horizontal (Vx) and vertical(Vy) components of the initial muzzlevelocity.
2. Determine the time the object will be in theair based on
a = (Vof - Voi)/t or d = Voyt + 1/2 at2a = -9.8 m/s2
3. Determine the distance the projectile willtravel horizontally using dx = Vixt
What is the Range of aProjectile
• How far will a projectile travelhorizontally if it is fired with a muzzlevelocity of 250 m/s at an angle of 45°above the horizontal?
Answer: 6390 m
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