1. Class Notes 24 September Turn in HW / Pick up HW Today:
Draw sketch, show your origin and coordinate system.
Start from the basic equations!
Include all subscripts in equations.
4d: a = –g the entire time.
Today:
Relative Velocity, Force

2. 45 degrees wins…if you can maintain the same speed.

3. Example
A small ball is shot into the air at an initial angle of 50.0º The ball hits the table 235 cm away and cm below the initial location. Determine the initial speed and the time of flight.
Use the first trigger place.
4.62 m/s, s

4. Projectile Motion Throw koosh ball Shoot toy cannon
Show parabolic connection
y=v0sinq0t –0.5gt2, x=vocosq0t 
y = tanq0x –0.5gx2/vo2 so,
y = Ax – Bx2 Parabola!

5. Relative Velocity vAC = vAB + vBC
The question “What is an object’s velocity?” implies a certain reference frame.
In 1D: Add. & subtraction
In 2D: Vector addition!
Examples…
vAC = vAB + vBC

6. Example
A river runs W to E at 3.00 m/s. A raft rows 4.00 m/s at 60.0º, relative to the water. What is the velocity of the raft as determined by people on the shore?
6.08 m/s at 34.7°

7. Dynamics: The Cause Isaac Newton (1642-1727)
Philosophiae Naturalis Principia Mathematica
Latin, 1687
Does NOT cover very fast,
very large, or very small
3 Laws of Motion (Chapter 4)
Law of Gravity (Chapter 5)
Dynamics: Students walk in room and I throw koosh ball. They notice the path, this is kinematics. They see who threw it, they are doing dynamics.

8. Homework Finish reading chapter 3 Do problems on worksheet #14
See canvas
TEST 2: This Friday!
Review sheet on Canvas
Chapters 1-3, esp. 2D motion
Quizzes online
Stress that for all relative velocity problems they MUST a) pick reference points, b) draw the representative vector diagram, c) label the corners, and d) write the associated vector formula.