Projectiles and Projectile Motion

What is a projectile?

A projectile is any object which once projected continues in motion by its own inertia and is influenced only by the downward force of gravity.

Examples

Projectiles Continued

Gravity influences a projectile’s vertical motion and causes the characteristic parabolic trajectory.

See these paths!!

Projectile Characteristics

There can be two components of the projectile's motion - horizontal and vertical.

"perpendicular components of motion are independent of each other" These two components of motion can (and must) be discussed separately.

The force of gravity does not effect the horizontal component of motion; a projectile maintains a constant horizontal velocity since there are no horizontal forces acting upon it.

Projectiles Described Mathematically

horizontal motion dx = vix t

vertical motion dy = viy t + 1\2gt2

Ex.1

A bullet is fired horizontally at 200.0 m/s from a height of 10.0 m. Calculate the following:

A) time of flightB) horizontal displacementC) the final velocity of the bullet ( recall

that velocity is a vector quantity and will need a direction)

Ex.2

A soccer ball is kicked horizontally off a 22.0-meter high hill and lands 35.0 meters from the edge of the hill. Determine the initial horizontal velocity of the soccer ball

Solution

Horizontal Information:dx = 35.0m, a = 0m/s2, vx = ?

Vertical Informationdy = -22.0m, viy = 0m/s, a = -9.81m/s2

Solution Continued

Use dy = viyt + ½ at2, to solve for time– Should get 2.12s

Then use dx = vx t, and solve for vx.– Should get 16.5m/s