Chapter 2 – Motion in Chapter 2 – Motion in One Dimension!One Dimension!

Oh my gosh…like…you’re so Oh my gosh…like…you’re so predictable!predictable!

1 dimensional motion1 dimensional motion

Think of a straight train route…Think of a straight train route…(can only move forward or backward…not up or (can only move forward or backward…not up or

down and side to side)down and side to side)

Displacement: As any object Displacement: As any object

moves from one position to another, the moves from one position to another, the length of the straight line drawn from the length of the straight line drawn from the initial to final position.initial to final position.

ΔX = Xf - Xi

displacement = change in position = final position – initial position

Things that make you go Things that make you go hmmm…hmmm…

A girl walks from the front of the class to A girl walks from the front of the class to the back of the class (20 ft). She then the back of the class (20 ft). She then walks back to the front of the class (20 ft). walks back to the front of the class (20 ft). What is her displacement when she has What is her displacement when she has finished walking?finished walking?

(Since we are only talking about 1-(Since we are only talking about 1-dimensional motion we can use the x or y dimensional motion we can use the x or y axis)axis)

More thought questions…More thought questions…

Does displacement always equal the Does displacement always equal the distance traveled?distance traveled?

Can displacement be positive or negative?Can displacement be positive or negative?

Shall we try?Shall we try?

VelocityVelocity

What is necessary to know velocity?What is necessary to know velocity? Avg. velocity: the displacement divided by Avg. velocity: the displacement divided by

the time interval during which the the time interval during which the displacement occurred.displacement occurred.

vavg = Δx = xf - xi

Δt = tf - ti

Can the average velocity be positive or Can the average velocity be positive or negative? negative?

What What part part of average velocity is ALWAYS of average velocity is ALWAYS positive?positive?

Practice makes us more perfect.Practice makes us more perfect.

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

Counterintuitiveness…Counterintuitiveness…

A train travels from Rome to Croatia (100 A train travels from Rome to Croatia (100 km). If the first half of the distance is km). If the first half of the distance is covered at 50 km/hr and the second half is covered at 50 km/hr and the second half is covered at 100 km/hr, what is the Vcovered at 100 km/hr, what is the Vavgavg??

Stop…Stop…Hammer Time! Only kidding, but Only kidding, but during this tune I want you to think. Treats during this tune I want you to think. Treats for someone who gets this correct!for someone who gets this correct!

Mucho examples aqui!Mucho examples aqui!

A book is moved once around A book is moved once around the edge of a table top with dimensions the edge of a table top with dimensions 1.75 m x 2.25 m. 1.75 m x 2.25 m.

If the book ends up at its initial position, If the book ends up at its initial position, what is its displacement? what is its displacement?

If it completes its motion in 23 s, what is If it completes its motion in 23 s, what is the average velocity? the average velocity?

What is it’s average speed?What is it’s average speed?

So you think you are smart?So you think you are smart?

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

Velocity isn’t always averageVelocity isn’t always average Instantaneous velocity: the velocity of an Instantaneous velocity: the velocity of an

object at some instant (or specific point in object at some instant (or specific point in it’s path).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 If it is a curved line, use the slope of the

tangent at that point.tangent at that point.

Graphing stuff…listen to Ms. O Graphing stuff…listen to Ms. O babble.babble.

It’s going to be on the ACT!!!!It’s going to be on the ACT!!!! Do practice problems on p.47 #1-5Do practice problems on p.47 #1-5 Now it’s time to design…HOLLA!Now it’s time to design…HOLLA!