Schedule

1. Schedule • Today: • 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. 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. Physics 253

3. 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? 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 Physics 253

5. V Vy=Vyj Vx=Vxi Vz=Vzk V = Vxi + Vyj + Vzk 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. Physics 253

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

8. Physics 253