Chapter 2 – Motion in One Dimension! Oh my gosh…like…you’re so predictable!

1 dimensional motion  Think of a straight train route… (can only move forward or backward…not up or down and side to side)  Displacement: As any object moves from one position to another, the length of the straight line drawn from the initial to final position. ΔX = X f - X i displacement = change in position = final position – initial position

Things that make you go hmmm…  A girl walks from the front of the class to the back of the class (20 ft). She then walks back to the front of the class (20 ft). What is her displacement when she has finished walking?  (Since we are only talking about 1- dimensional motion we can use the x or y axis)

More thought questions…  Does displacement always equal the distance traveled?  Can displacement be positive or negative?  Shall we try?

Velocity  What is necessary to know velocity?  Avg. velocity: the displacement divided by the time interval during which the displacement occurred. v avg = Δx = x f - x i Δt = t f - t i

 Can the average velocity be positive or negative?  What part of average velocity is ALWAYS positive?

Practice makes us more perfect.  Example: You take a trip in your ______ to a friend’s ______ 370 km to the west (negative direction). If you left your ______ at 10 a.m. and arrived at your friend’s ______ at 3 pm, what would your average velocity be?

Counterintuitiveness…  A train travels from Rome to Croatia (100 km). If the first half of the distance is covered at 50 km/hr and the second half is covered at 100 km/hr, what is the V avg ?  Stop…Hammer Time! Only kidding, but during this tune I want you to think. Treats for someone who gets this correct! Hammer Time!Hammer Time!

Mucho examples aqui!  A book is moved once around the edge of a table top with dimensions 1.75 m x 2.25 m.  If the book ends up at its initial position, what is its displacement?  If it completes its motion in 23 s, what is the average velocity?  What is it’s average speed?

So you think you are smart?  Heather travels from New York to Miami to catch up with the cast of Jersey Shore at a speed of 25 m/s. Robiane travels from New York to Chicago because New York is smelly, also at a speed of 25 m/s. Are the velocities of these girls equal? Explain.

Velocity isn’t always average  Instantaneous velocity: the velocity of an object at some instant (or specific point in it’s path). If it is a straight line graph, use the slope. If it is a straight line graph, use the slope. If it is a curved line, use the slope of the tangent at that point. If it is a curved line, use the slope of the tangent at that point.

Graphing stuff…listen to Ms. O babble.  It’s going to be on the ACT!!!!  Do practice problems on p.47 #1-5  Now it’s time to design…HOLLA!