1. Projectile motion
2-dimensional motion of an object launched non-vertically
Falls freely (neglect air resistance unless I tell you otherwise)

2. Imagine shadow of ball on the wall…. …on the ground
Only y motion has acceleration, force
Imagine shadow of ball on the wall…. …on the ground

3. P1. Bob is loading his gun while Fred suddenly shoots his gun horizontally. Bob drops his bullet the instant Fred fires. Whose bullet hits the ground first (from same height)?
a. Bob’s
b. Fred’s
c. at same time
Demo: monkey-hunter

4. x and y motions are connected by the time it takes to complete the path!
Hints for projectile motion:
Draw pictures, label variables. Decide +y direction
Determine initial velocity components
If t is not given, identify which coordinate motion has the information to give the total free-fall time, and find t.
Find other needed quantities from kinematic eqns.

5. In this example, the time in the air is the same as that of a ball____
A rock is ejected at an angle of 35o above horizontal, at 25 m/s, from a 20 m high volcano. How far from the volcano does it land?
In this example, the time in the air is the same as that of a ball____
rolled at 25 m/s along the ground for 20 m
thrown vertically at 25 m/s, hitting the ground 20 m below
thrown vertically at 25cos(35) m/s, hitting the ground 20 m below
thrown vertically at 25sin(35) m/s, hitting the ground 20 m below
dropped vertically, hitting the ground 20 m below

6. In this example, the time in the air is the same as that of a ball____
rolled at 20 m/s along the ground for 50 m
rolled at 20cos(40) m/s along the ground for 50 m
rolled at 20sin(40) m/s along the ground for 50 m
thrown vertically at 20cos(40) m/s, hitting the ground 50 m below
thrown vertically at 20sin(40) m/s, hitting the ground 50 m below

7. In this example, the time to fall is the same as that of a ball that ….

8. Find final velocity components
Final speed
Final velocity angle

9. P2. A battleship simultaneously fires two shells at enemy ships
P2. A battleship simultaneously fires two shells at enemy ships. If the shells follow the parabolic trajectories shown, which ship gets hit first? A. A B. B C. same

10. P3. Which spends the longest time falling?
Sally and Bob each throw a rock horizontally from a cliff. Sally throws her rock hard. Bob throws his more easily.
P3. Which spends the longest time falling?
A. Sally’s
B. Bob’s
C. same
P4. Which rock is going fastest (vector magnitude) just before it hits the ground?
P5. Sally throws a rock horizontally from a cliff. Bob throws his at an angle above horizontal. They throw the same speed. Which hits first?

11. P6. A man on a moving railroad car shoots exactly vertically at a bird which is directly over him and moving at the same constant horizontal velocity (no air resistance)
His shot will go behind the bird
He will hit it
His shot will go ahead of the bird

12. What happens if he misses?

13. Lecture 4, projectiles Basic concepts: Basic problems, skills:
x and y motion are independent, except connected by time
x motion is that of a ball moving at constant speed
y motion is that of a ball thrown up, down or dropped along y
Basic problems, skills:
horizontal launching
deciding when x or y motion determines when freefall ends
Advanced concepts:
effect of initial vy
Advanced problems, skills:
nonhorizontal launching
finding final v from components
solving when vi or q is not given