2.3 Projectile Motion How would you describe the motion of an Olympic ski jumper as she begins her jump off a ramp? The motion of a ski jumper is identical to that of a ball being thrown forward in the air. Both travel through a two-dimensional curved path called a parabola. A projectile is an object that moves along a curved 2-D trajectory (path), under the influence of gravity. The motion of a projectile under gravity is called projectile motion.

What Will Happen? Imagine you have two rubber balls, one in each hand...a red ball and a yellow ball. If you were to throw the yellow ball horizontally, and simply drop the red ball, from the same height, which ball would hit the ground first? Both balls would hit the ground simultaneously! (of course air resistance is negligible) Why does this occur?

2.3 Projectile Motion The white horizontal lines represent equal time intervals between the camera’s flashing strobe. Notice the vertical components of displacement for both balls increase with time by the same amount. Both balls experience the same vertical motion. As a result, both balls reach the ground at the same time.

2.3 Projectile Motion When analyzing projectile motion, the horizontal motion (x-dir) and the vertical motion (y-dir) are independent of one another. The horizontal and vertical motions of a projectile take the same amount of time. Vertically, projectiles accelerate due to gravity. The force of gravity acts downward. Since no force is acting on a projectile horizontally, it moves at a constant velocity in the x-direction.

Solving Projectile Motion Problems

SP # 1 p.77

2.3 Homework Practice # 1,2 p.78 Questions #1,2,5,8* p.81