PHYS16 – Lecture 3 Physics of 1D Motion Friday, September 10, 2010 Looney Tunes

Administration Vectors Review from last week Key Concepts – Physics 1D motion Displacement, Velocity, & Acceleration Agenda

Register Clickers Textbook – University Physics vol. 1 by Bauer & Westfall Connect Physics – Math Exam Homework Assignments – On course website – On Connect website Administration

Review from last week Significant figures – Every digit that has meaning (not trailing or leading zeros) – has 3 significant figures – When multiply/divide keep # of sig figs of number with lowest amount of sig figs – When add/subtract keep # to the lowest decimal Scientific Notation – Way of expressing number with sig figs and order of magnitude – 12,300,000 is 1.23E7 Units – Know prefixes – milli = 10^-3, kilo=10^3 – Conversion If 1 M = 1 mol/L then 4.0 mol in 3.0 L is? 4.0 mol/3.0 L = 1.3 M If 25.4 mm = 1 in then 3.2 in = mm? 3.2 in*25.4 mm/in= 81 mm

Vectors Vector vs. Scalar – Vector – quantity with both magnitude and direction – Scalar – quantity with just magnitude Which is a vector and which is a scalar? – 25 apples in a bucket(scalar) – Car coming at me at 100 mph(vector) – I live 6 miles from grandma(scalar) – Grandma’s house is 6 miles east of here(vector)

Vector Representation Finding Vector components – Use Trig!!!

Math Review Questions 1 Let’s say we make a measurement of our position with 3 different GPS devices (GPS watch, GPS phone, and a car GPS) and we know that we are right next to the bank (red x). Which GPS is the most ACCURATE? A.GPS watch B.GPS phone C.Car GPS BANK GROCERY

Math Review Questions 2 Let’s say we make a measurement of our position with 3 different GPS devices (GPS watch, GPS phone, and a car GPS) and we know that we are right next to the bank (red x). Which GPS is the most PRECISE? A.GPS watch B.GPS phone C.Car GPS BANK GROCERY

Math Review Questions 3 A problem asks you to find the pressure (P) a piston exerts given a force (F) of 23.7 N and a length (l) and width (w) of the piston of 11 cm and km, respectively. The equation that governs this is P=F/(lw). How many significant digits should you enter in your answer? A. 1 B. 2 C. 3 D. 4 E. There is not enough information.

Math Review Questions 4 A problem asks you to find the pressure (P) a piston exerts given a force (F) of 23.7 lbs and a length (l) and width (w) of the piston of 11 in and in, respectively. The equation that governs this is P=F/(lw). What are the units of pressure? A.lbs B. in C. lbs/in D. lbs/(in^2) E. There is not enough information.

Math Review Questions 5 What is the value for V 3 ? A.(4,4) B.(-2,2) C.(2,-2) D.(3,3) E.(4,3) V 3 =? V 2 = (1,3) V 1 = (3,1)

Key Concepts: Physics 1D Motion Displacement, Velocity, & Acceleration – Know the definitions of these terms – Know how they are related Motion with Constant Acceleration – Solve the equations of Motion for constant accel. – Know the 5 kinematic equations – Use the kinematic equations to solve problems

Displacement Displacement vs. Distance – Displacement = final position – initial position with both magnitude and direction – Distance = total position traversed from final position to initial position, just magnitude

Velocity Velocity vs. Speed – Velocity – final position minus initial position divided by time, both magnitude and direction – Speed – how fast you are going, just magnitude 60 mph

Acceleration – Final velocity minus initial velocity divided by time, both a magnitude and a direction – How much an object speeds up or slows down com Position graph where acceleration is not 0

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

For Next Time… Online homework due Tuesday Online lab homework due Wednesday Online Math Exam due Sunday Get your clicker, text, connect access…