PHYS 16 Lecture 4 Looney Tunes Motion Ch

PHYS 16 – Lecture 4 Looney Tunes Motion Ch. 2 Motion in 1 D

Before we begin… this class is different • My role vs. your role – My role… Guide, Resource, Demonstrator – Your role… Thinker, Inquisitor, Observer • The role of homework – Physics is about trying to describe our world with a set of mathematical equations – Homework is not regurgitating information • Cracking the problem – which eqs. /concepts to use • Solving the problem – apply the math correctly

Motion • Ch. 2 Motion in 1 D – Position, Velocity, and Acceleration – Free Fall • Ch. 4 Motion in 2 D – Projectile Motion – Relative Motion

Intro – Motion pre-question • If a 0. 50 kg ball is launched straight up and is given an initial velocity of 15 m/s, what will be the velocity of the ball on the way back down at the launch point? (Note: assume air resistance is negligible and that g=9. 8 m/s 2. ) A) It is the same as when it was launched. B) It is dependent on initial velocity. C) It is dependent on the acceleration constant. D) It is dependent on the angle it was shot at. E) None of the above

Displacement, Velocity, Acceleration

Displacement • Displacement vs. Distance – Displacement = change in position – Distance = total position traversed

Velocity • Velocity vs. Speed – Avg. Velocity – – Avg. Speed – – Inst. Velocity – – Inst. Speed – Can the magnitude of average velocity ever equal the average speed?

Acceleration • Acceleration – Avg. Acceleration – – Inst. Acceleration – Position graph where acceleration is not 0 http: //physics 247. com

Displacement, Velocity, Acceleration X V a

Demo: Remote Control Car http: //familycourtchronicles. com

Questions • Can displacement be zero and distance be Yes positive? No • Can distance ever be negative? No • Can speed ever be negative? Yes • Can acceleration be negative? • Can an object that is stopped at t=0 have a Yes positive acceleration? • If an object is traveling at a constant velocity can it have an acceleration? No

Free Fall

Free Fall • Object under influence of the Earth’s gravity is in free fall • Dropped, thrown up, thrown down -> acceleration due to gravity is the same • g=9. 80 m/s 2, ay=-g

Derive Kinematic Equations

Conclusions • Displacement and Distance are different! • Avg. Speed is NOT the magnitude of Avg. Vel. • Displacement -> Velocity -> Acceleration (take derivatives) • Const. acceleration gives the three equations