1. Projectile Motion Section 7.2
Physics

2. Objectives
Recognize that the vertical and horizontal motions of a projectile are independent.
Relate the height, time in the air, and initial vertical velocity of a projectile using its vertical motion, then determine the range.
Explain how the shape of trajectory of a moving object depends upon the frame of reference from which it is observed.

3. What is a projectile?
Pro – jec - tile: a body projected or impelled forward, as through the air.

4. Types of Projectiles Dropped straight down. Thrown straight up.
Thrown with a horizontal and vertical velocity.

5. Plane of Motion for a Projectile

6. Independence of Motion in Two Dimensions
Horizontal motion does NOT affect the vertical motion.
/gravitational_acceleration/horizontal_and_vertical_ball_drop.gif

7. Constant Horizontal Motion
Horizontal motion is constant because it is initiated by a contact force.
Vertical motion is not constant because it is caused by a long-range force.

8. How do we draw a projectile’s motion?
Horizontal and vertical arrows indicate respective velocities: vx & vy.
The velocity vector is the combined vector of the x and y components.

9. Projectiles Launched Horizontally
Projectiles launched horizontally have no initial vertical velocity.
Their vertical motion is identical to that of a dropped object.
Downward velocity increases regularly because of acceleration due to gravity.

10. No Initial Vertical Velocity

11. Practice Problems
Pg 158
9-11

12. Projectiles Launched at an Angle.
When a projectile is launched at an angle, the initial velocity has vertical and horizontal components.
Starts with highest vertical velocity, reaches its peak where velocity is zero, and descends with increasing speed.

13. Projectiles Launched at an Angle
Maximum height: height of the projectile when the vertical velocity is zero and the projectile has only its horizontal velocity component.
Range, R: horizontal distance the projectile travels.
Flight-time: time the projectile is in the air.

14. Projectiles Launched at an Angle

15. Practice Problems
Pg 160
12-13

16. Air Resistance and Projectiles
Air resistance affects projectiles.
Golf ball dimples.
Spin of a Baseball due to laces.
Frisbee.
Boomerang.