1. Schedule Today: Friday Feb 9th: Monday Feb 12th:
Review of Material in Quiz 1 on Units 1 and 2
Start Unit 3: Force and the Laws of Motion
Friday Feb 9th:
No class, use the time to study for the test
Monday Feb 12th:
Quiz #1
Problem sets for Units 1 and 2 due.
1/18/2019
Physics 253

2. Material to Master Unit 1: Measurement and Motion
How to assign significant figures and calculate relative uncertainty.
Conversion of units.
Use of dimensional analysis.
The equations of motion for constant acceleration.
Analysis of problems in free-fall.
Unit 2: Vectors and 2-D Motion
Unit vectors and vector addition.
The equations of motion for projectile motion
Analysis of problems of projectile motion.
1/18/2019
Physics 253

3. Read & access the problem
Setup
Read & access the problem
Draw a diagram with coordinate system, choose + and - directions
Create a table of known and unknown quantities
Manipulation of Equations
Consider the physics involved
Select appropriate equation or equations
Do required calculations
Check you work
Does it pass the smell test
Do the units make sense?
1/18/2019
Physics 253

4. Idealized motion (where air resistance is neglected and the acceleration is constant) is known as freefall.
The magnitude of the acceleration due to gravity at the earth’s surface is denoted:
Since the acceleration is constant we can apply the equations of motion!
Because objects fall in the vertical or y direction it's also natural to use the symbol y for displacement
g = 9.80 m/s2 or 32.2 ft/s2
1/18/2019
Physics 253

5. Vy=Vyj
Vx=Vxi
Vz=Vzk V
V = Vxi + Vyj + Vzk
1/18/2019
Physics 253

6. Power of Unit Vectors Now it’s a snap to add and subtract vectors!
One just adds the coefficients of the units vectors.
Later on we’ll learn about other key operations that are facilitated by unit vectors such as dot and cross products.
1/18/2019
Physics 253

7. Kinematic Equations for Projectile Motion (+y up, ax =0, ay=-g= -9
Kinematic Equations for Projectile Motion (+y up, ax =0, ay=-g= -9.8m/s2
1/18/2019
Physics 253

8. 1/18/2019
Physics 253