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Over the Edge. Horizontal Projectiles. A red ball rolls off the edge of a table. Describe the path it takes as it falls. Parabolic Path. As the red ball rolls off the edge, a green ball is dropped from rest from the same height at the same time. Which one will hit the ground first?.
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Over the Edge Horizontal Projectiles
A red ball rolls off the edge of a table Describe the path it takes as it falls Parabolic Path
As the red ball rolls off the edge, a green ball is dropped from rest from the same height at the same time Which one will hit the ground first? They will hit at the SAME TIME!!!
The SAME time??? How? The green ball falls from rest and has no initial velocity IN EITHER DIRECTION! viy and vix = 0 The red ball has an initial HORIZONTAL velocity (vix) But does not have any initial VERTICAL velocity (viy = 0) vix
One Dimension at a Time • Both balls begin with no VERTICAL VELOCITY • Both fall the same VERTICAL DISTANCE • Both experience the same GRAVITATIONAL ACCELERATION • Therefore, they hit at the same time!
Horizontal Projectile Rules • The Horizontal and Vertical Axes are INDEPENDENT OF EACH OTHER • X values stay in the x-axis • Y values stay in the y-axis • But TIME links them together! • X-Axis • ax= 0m/s2 • vix = vfx • Y-Axis • viy= 0m/s • ay = -9.81m/s2
Example #1 • A bullet is fired horizontally from a gun that is 1.7 meters above the ground with a velocity of 55 meters per second. At the same time, the shooter drops an identical bullet from the same height. • Which bullet hits the ground first? • Calculate the horizontal distance the bullet traveled Both hit the ground at the same time Find time using the Y-Axis FIRST – 2 Step Problem!
Example #1 Continued Y-Axis
Example #1 Continued X-Axis
Example #2 • An airplane making a supply drop to troops behind enemy lines is flying with a speed of 300 meters per second at an altitude of 300 meters. • How far from the drop zone should the aircraft drop the supplies?
Example #3 • A stuntman jumps off the edge of a 45 meter tall building to an air mattress that has been placed 15 meters from the edge of the building on the street below. • Calculate the minimum initial velocity he needs to reach the air mattress.
Example #4 • A CSI detective investigating an accident scene finds a car that has flown off the edge of a cliff. The car is 79 meters from the edge of the 25 meter high cliff. • How fast was the car going as it went off the edge?
SUMMARY • Which object will land first? An object launched horizontally or an object dropped from the same height? • List the two rules for the X-AXIS • List the two rules for the Y-AXIS • Which axis are you usually in to find time?