Ch. 6 Motion in Two Dimensions Projectile Motion

Any object moving through the air and affected only by gravity is called a projectile  flying objects such as airplane and birds are not projectile because they are affected by other forces The path a projectile follows is called its trajectory  trajectories are a special type of arch called a parabola The range of a projectile is the horizontal distance the object travels before it hits the ground A projectiles range depends on the speed and angle at which it is launched

Horizontal and vertical motion Projectile motion is 2 dimensional  both motions happen at the same time The motion is easiest to understand by looking at the horizontal (x) and vertical (y) motion separately. The horizontal and vertical components of a projectile's velocity are independent of each other  the horizontal component does not affect the vertical component and vice versa

A projectile at any one point has both a horizontal (v x ) and vertical (v y ) component (velocity)  always be sure to identify velocities in either the v x or v y Vertical motion projectileHorizontal motion projectile

Horizontal (v x ) component A ball rolling off a table is considered a projectile once it leaves the tabletop Once it becomes a projectile, it no longer feels a horizontal force  instead, its velocity remains constant Ex. The balls horizontal velocity is 5m/s  this means that the ball will move a distance of 5 meters every second -the balls horizontal motion will continue moving the same way it would if it were rolling on the ground The vertical distance of a projectile travels would be calculated the same way as if it were on the ground  d=sxt

Vertical (v y ) component Gravity (g) is the force acting on projectiles in the vertical motion just as in free fall  the vertical speed increases by 9.8m/s every second The vertical distance the ball falls can be made using one of the kinematic equations d=1/2at 2 or

Calculating Projectile Motion PracticeProjectile Motion Time(s) dxdx dydy vyvy V x = 6 m/s t =0 s t =2 s t =4 s 5

Practice Problem #1 1.) You kick a soccer ball and it travels a horizontal distance of 12 meters during the 1.5 seconds it is in the air. What was the ball’s initial horizontal speed?

Practice Problem #2 2.) A stunt driver steers a car off a cliff at a speed of 20 m/sec. He lands in the lake below two seconds later. Find the horizontal distance the car travels and the height of the cliff.

Practice Problem #3 A ball is pushed off a cliff at a speed of 9.5 m/sec. It lands in the lake below three seconds later. Find the horizontal distance the ball travels and the height of the cliff.