1. UNIT 2 Two Dimensional Motion
And Vectors

2. ConcepTest 3.5 Dropping a Package
1) quickly lag behind the plane while falling
2) remain vertically under the plane while falling
3) move ahead of the plane while falling
4) not fall at all
You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the package will:
[CORRECT 5 ANSWER]

3. ConcepTest 3.5 Dropping a Package
1) quickly lag behind the plane while falling
2) remain vertically under the plane while falling
3) move ahead of the plane while falling
4) not fall at all
You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the package will:
Both the plane and the package have the same horizontal velocity at the moment of release. They will maintain this velocity in the x-direction, so they stay aligned.
[CORRECT 5 ANSWER]
Follow-up: What would happen if air resistance is present?

4. ConcepTest 3.6b Dropping the Ball II
1) the “dropped” ball
2) the “fired” ball
3) neither – they both have the same velocity on impact
4) it depends on how hard the ball was thrown
In the previous problem, which ball has the greater velocity at ground level?

5. ConcepTest 3.6b Dropping the Ball II
1) the “dropped” ball
2) the “fired” ball
3) neither – they both have the same velocity on impact
4) it depends on how hard the ball was thrown
In the previous problem, which ball has the greater velocity at ground level?
Both balls have the same vertical velocity when they hit the ground (since they are both acted on by gravity for the same time). However, the “fired” ball also has a horizontal velocity. When you add the two components vectorially, the “fired” ball has a larger net velocity when it hits the ground.
[CORRECT 5 ANSWER]
Follow-up: What would you have to do to have them both reach the same final velocity at ground level?

6. Projectiles: Launch At Any Angle
Monday September 26
Projectiles: Launch At Any Angle

7. TODAY’S AGENDA UPCOMING… Projectile Motion
Monday, September 26
Projectile Motion
Mini-Lesson: Launch At Any Angle
Hw: Complete Practice D Problems (all)
UPCOMING…
Tues: LAB 3: Projectile Motion
Wed: More Projectile Motion
Thurs: the Boards
Fri: Problem Quiz 2 Projectile Motion
Access to Reading Quizzes 11:30pm
Mon: the Boards
Tues: CH 3 TEST

8. Demonstration with MythBusters
Demonstration with Dr. Walter Lewin

9. General Launch Angle

10. General Launch Angle

11. Resolving the Velocity

12. Resolving the Velocity

13. Projectile Motion Equations
Horizontal
Velocity
Eq 2
Vertical
Velocity
Eq 3
Eq 4
Horizontal
Displacement

14. Projectile Motion Equations
Vertical
Displacement
Eq 6
Range
Eq 7
Time to
the Top

15. Consider the Range equation:
Sample Problem
A golfer hits a golf ball at an angle of 25.0˚ to the ground. If the golf ball covers a horizontal distance of m, what is the ball’s maximum height?
(Hint: At the top of its flight, the ball’s vertical velocity component will be zero.)
Consider the Range equation:
Solve for the
Now find time to the top:

16. Find the vertical height at 2.68 s:

17. Sample Problem
A potato is shot from a potato gun at m/s at an angle of 45.0˚. The potato is shot from a bridge 50.0 m above the water. Find the following:
a) total time of flight
b) final velocity just before hitting the water
c) total horizontal displacement
d) maximum vertical displacement above the water

18. Break the initial velocity into x- and y- components.
What must I do first?
Break the initial velocity into
x- and y- components.
Which question is easiest to answer?
Find the total time of flight
Which equation has all the information but time?
By quadratic equation, t = 15 s

19. Without the quadratic formula solve for t:
2 STEPS:
Find final velocity in y-axis
Find time

20. What is the final velocity?

21. What is the total horizontal displacement?
What is the maximum vertical displacement above the water?

22. Sample Problem
.82 s

23. END