Unit Two Chapter 3, Part 2 Projectile Motion

A projectile is an object upon which the only force acting is gravity

Realize……. that the only force acting upon an upwardly moving projectile is gravity.

Don’t be fooled by the common misconception that a force is required to keep an object in motion. A force is not required to keep an object in motion. A force is only required to maintain an acceleration.common misconception

Or….. Without gravity, you could launch a banana straight at a monkey in a tree. Notice: the monkey does not fall when he catches the banana because there is no gravity

But with gravity……

In the presence of gravity, the monkey also accelerates downward once he lets go of the limb. Both banana and monkey experience the same acceleration since gravity causes all objects to accelerate at the same rate regardless of their mass.

Gravity is the downward force upon a projectile which influences its vertical motion and causes the parabolic trajectory which is characteristic of all projectiles.

Characteristics of Projectiles 1. Projectiles always maintain a constant horizontal velocity (neglecting air resistance)

2.Projectiles always experience a constant vertical acceleration of 10.0 m/s 2 downward. (neglecting air resistance)

3.Horizontal and vertical motion are completely independent of each other. Therefore, the velocity of a projectile can be separated into horizontal and vertical components.

4.For a projectile beginning and ending at the same height, the time it takes to rise to its highest point equals the time it takes to fall back to its original position….

5.Objects dropped from a moving vehicle have the same velocity as the moving vehicle.

The distance any projectile goes is: d = 5 t 2

So when we are measuring the distance we are measuring downwardness and sidewaysness of the projectile

Satellites – projectile traveling fast enough to fall around the earth rather than onto it.

Launch Speed less than 8000 m/s Projectile falls to Earth

Launch Speed equal to 8000 m/s Projectile orbits Earth - Circular Path

Launch Speed greater than 8000 m/s Projectile orbits Earth - Elliptical Path