2 D Projectile Motion Ball Drop Demo 1

2 -D Projectile Motion

Ball Drop Demo 1. Which marble will hit the ground first? Why? 2. Which marble will have the higher velocity when it hits the ground? Why? 3. Which marble is a projectile? Explain.

Strobe of Falling Ball Question: If an expert military marksman were to fire his sniper rifle horizontally and at the same time drop a bullet from the same height of the gun (so that both bullets are falling the same vertical distance), which bullet would hit the ground first? Bullet Myth

• The horizontal motion of a projectile does not depend on the vertical motion • This means we treat the two parts of a projectile’s motion separately, independent of each other

• Remember, Gravity is the only force acting on a projectile – Gravity always acts downward – There is NO horizontal force

Horizontal Distance (in the x direction) ( dx ) is called the range d x = vx t

• A cannonball is launched horizontally off a cliff with an initial velocity of 100 m/s. The cannonball takes 12 seconds to land. 1. How high is the cliff? 2. What is the vertical velocity of the cannonball when it hits the ground? 3. What is the horizontal velocity of the cannonball when it hits the ground? 4. What is the range of the cannonball?

If a projectile is launched horizontally We know (when no air resistance): • The initial vertical velocity will be zero • The time it will take for the projectile to land is the same as if it were dropped from rest • Once launched, gravity is the only force acting on it