Horizontal Projectiles

PhysicsMrs. Coyle

Horizontal Projectiles are launched with a horizontal initial velocity.

Horizontal Projectiles

http://www.physicsclassroom.com/mmedia/vectors/hlp.cfm

Remember “Boat and River”

Motion in Two Dimensions

http://www.physicsclassroom.com/mmedia/vectors/hlp.cfm

Which falls first?

A free falling object

Or

A horizontal projectile from the same height

Which falls first?

A horizontal projectile

Or

A horizontal projectile from the same height with a higher initial

horizontal speed

Question

A zoologist is aiming at a monkey with a tranquilizer gun. Both are at the same level. The monkey is about to jump. Should the zoologist aim horizontally or low in order to tranquilize the monkey?

Horizontal Projectiles

Two dimensional motion

Initial velocity is entirely horizontal

X-axis : constant velocity

Y-axis : constant acceleration

A Look at the Velocities

Vx= constant

Vyi=0

Vy = a t

Animation

http://www.physicsclassroom.com/mmedia/qt/vectors/hlpwin.cfm

Characteristics of Path

Trajectory

Parabola

Range

Equations for Horizontal Projectiles

x direction: use any equation for const. velocity motion

y direction: use any equation for const acceleration

x=vx t ____

y= 1 at2 t= √2y/a 2 vY=at

Example 1

A cannon ball is fired horizontally from the top of a 90 m tall cliff with an initial velocity of 20 m/s.

a) How long did the ball take to reach the ground?

b) What was the range?c) What was the x and y-velocity of the ball right

before it hit the ground?

Answer: a)4.3sec , b) 85.7m c) Vx= 20m/s Vy=42m/s

Example 2

A diver dives horizontally out from a 9 mplatform with a velocity of 3m/s. How farout did he dive (range)?

Answer: t=1.35s, x= 4m

http://www.walter-fendt.de/ph11e/projectile.htm

Projectile Applet