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3.3 Projectile Motion. From Ch 3 – Two dimensional Motion and Vectors. Half Projectile. Vx t D y D x. Equations. D y = ½ g t 2 or t = sq rt 2 D y / g g = -9.81 m/s 2 D x = Vx t (Vx is constant). Example of Half Projectile.
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3.3 Projectile Motion From Ch 3 – Two dimensional Motion and Vectors
Half Projectile • Vx t Dy Dx
Equations Dy = ½ g t2or t = sq rt 2 Dy / g g= -9.81 m/s2 Dx = Vx t (Vx is constant)
Example of Half Projectile People in movies often jump from buildings into pools. If a person jumps horizontally form the 10th floor (30.0 m) to a pool that is 5.0 m away from the building with what initial speed must the person jump? Dy = 30.0 m Dx = 5.0 m Vx = ?
Find t and then Vx t = sq rt 2 Dy / ag t = sq rt 2 (-30.0m) / -9.81 m/s2 t = sq rt 6.1 s t = 2.4 s Dx = Vx t or Vx = Dx / t Vx = 5.0 m / 2.4 s = 2.1 m / s Practice Activity: Homework WS and pg 99 1-3
Anatomy of a Full Projectile Vi 2 = Vx 2 + Vy2 Vx = Vi cos q Vy = Vi sin q Vi Vy Vx
More Anatomy Dx = Vx t Dy = (vi sin q) t + ½ at2 ttot = 2 ( Vy / g) t Dy t D X
Equations for a Full Projectile • Vi 2 = Vx 2 + Vy2 Vx = Vi cos q = constant Dx = (Vi cos q) t or DX tot = Vx ( t tot) • t tot = 2 ( Vy / g)
A Projectile is fired at an angle of 53o with the horizontal. The speed to the projectile is 200. m /s. A. Calculate the time the shell in air and the horizontal distance it travels.B. Calculate the maximum height reached. Sin 53o = Vy / 200 Vy = 159.7 m/s ttot= 2 X 159.7 / 9.81 = 32.56 = 32.6 s • Cos 53o = Vx / 200 • Vx = 120.36 = 120. m/s • Dxtot = 120 ( 32.6) = 3912 m • Dy = (159.7 m/s) 16s + ½ (-9.81 m/s2) (16 s)2 = 1300 m
Relativity Our perspective is that we are stationary and everything else is moving. When you are driving down the road and someone pulls up next to you they look like they are not moving. You are going at the same velocity ( same speed and direction)
Relativity When a car is coming directly at you. You attribute your speed to them. The red car is traveling at 50 mph and the blue car is traveling at 60 mph. It appears as if the other car is traveling at 110 mph toward you.
RelativityYou are riding in a car and look and see a person standing along side the road. The guy appears to be moving but in the opposite direction you are traveling.
Wrap Up • Review sheet is due • Marble Activity • Test