1. Unit 2, Lesson 8: Projectile Motion

2. Projectile Motion
Thought experiment: If you shoot a bullet horizontally from your gun and drop another bullet from the same height at the same time, which bullet hits the ground first?
A first
B first
Both at the same time B A
*Demo: golf ball and ping ball.
Downward acceleration due to gravity is constant!

3. Example 1
One of those old VW bugs is driven off a 50 m tall cliff at 108 km/h
How long is it in the air?
How far from the cliff does it land?
What is its velocity just before impact? (ignore air resistance)
50m
Note: horizontal and vertical motion is independent and we can look at each separately.

4. “falling straight down from rest”
“Moving straight right at 108 km/h, or 30 m/s” (constant speed)
Find the time for something to fall (from rest) 50 m
How far does something go at 108 km/h for 3.19 s? (constant speed)
10 min

5. c) What is its velocity just before impact? (ignore air resistance)
30m/s ө
31.36m/s v

6. Brain Break!
 35 min

7. Example 2
A Honda Civic with a 5000 Watt stereo is driven off a cliff at 25 m/s and lands 60 m from the base of the cliff. How high is the cliff?
10 min
60m
Answer: 28 m tall
HW: p113 #20-28

8. Homework:
Projectile Motion Problem Set #1-3
20 min

9. Unit 2, Lesson 9: More Projectile Motion

10. Warm-Up Question
Ashley throws a chone from a high cliff horizontally at 25 m/s. Find its velocity when it is 120 m below the top of the cliff.
25m/s
120m v?
vv?
25m/s
15 min

11. Brain Break!

12. Do #4-6 on the Projectile Motion Problem Set.
If you finish, try the following challenge problem:
A soccer ball is kicked from ground level with an initial velocity of 25 m/s at an angle of 37 above the horizontal. Find:
the horizontal and vertical components of the initial velocity.
how far away does the ball land?
what is the maximum height reached by the ball?
what is the velocity of the ball 2.0 seconds after it is kicked?
Answers:
a) vertical is 15 m/s and horizontal is 20 m/s
b) 62 m
c) 11.5 m
d) 20.5 m/s, 13 below the horizontal
40 min