F08_Lect02 - Physics 112: Lecture 2 Agenda for Today 1-D...

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Unformatted text preview: Physics 112: Lecture 2 Agenda for Today 1-D Kinematics 1-D Kinematics Average & instantaneous velocity and acceleration Motion with constant acceleration Motion in 1 dimension In 1-D, we usually write position as x(t). Since its in 1-D, all we need to indicate direction is + or . Displacement in a time t = t 2- t 1 is x = x(t 2 ) - x(t 1 ) = x 2- x 1 t x t 1 t 2 x t x 1 x 2 some particles trajectory in 1-D 1-D kinematics t x t 1 t 2 x x 1 x 2 trajectory Velocity v is the rate of change of position Average velocity v av in the time t = t 2- t 1 is: t V av = slope of line connecting x 1 and x 2 . v av " x ( t 2 ) # x ( t 1 ) t 2 # t 1 = $ x $ t Consider limit t 1 t 2 Instantaneous velocity v is defned as: 1-D kinematics... t x t 1 t 2 x x 1 x 2 t so v(t 2 ) = slope of line tangent to path at t 2 . v ( t ) = dx ( t ) dt You are driving on a highway at 80 km/h for 5 h and then through a town at 20 km/h for 30 minutes. What is your average velocity (assume that its all in one direction)? Average velocity: a common mistake Average velocity: a common mistake You are driving on a highway at 80 km/h for 5 h and then through a town at 20 km/h for 30 minutes. What is your average velocity (assume that its all in one direction)? Wrong: (v1 + v2)/2 = 50 km/h Correct: total distance / total time = (400 km + 10 km) / (5 h + 0.5h) = 74.5 km/h Graph of x(t) versus time, whats the average velocity? Defnition oF SPEED: distance traveled...
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This note was uploaded on 09/29/2008 for the course PHYS 1112 taught by Professor Leclair,a during the Fall '07 term at Cornell University (Engineering School).

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F08_Lect02 - Physics 112: Lecture 2 Agenda for Today 1-D...

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