Chapter 2 Motion in One DimensionSection 1Displacement and Velocity

Motion Motion happens all around us in different

directions and different speeds. One – dimensional motion is the simplest form of

motion. Example : Commuter train can move only forward

and backward along the straight track.

Frame of Reference Motion takes place over time and

depends on frame of reference. Frame of Reference – what you use to

measure changes in position.

Displacement Displacement is a change in position. (Final – Initial)

Displacement is NOT the same as distance traveled.

Displacement has a direction. Right and Up is (+) Left and Down is (-)

Displacement

Displacement

Velocity

Average Velocity is displacement of an object (Δx) divided by time interval (Δt).

Average Velocity can be positive or negative depending on the sign of the displacement.

If displacement is negative, avg. velocity is negative.

Time interval is ALWAYS positive

Guided Practice Open Books to pg. 44

Velocity is not the same as speed.

Velocity describes motion with direction and magnitude (numerical value);

Speed ONLY has magnitude.

Ex: 55 m/s and 55 m/s North

Velocity Vs. Speed

Velocity can be interpreted graphically…

The motion of an object moving with constant velocity will provide a straight-line graph of position versus time. The slope of this graph indicates the average velocity.

Section 2 Acceleration

Chapter 2One Dimensional Motion

2-2 Acceleration Acceleration measures the

rate of change in velocity. Has Magnitude & Direction. SI Units : m/s2

Three ways to Accelerate:

Object Speeding Up

Object Slowing Down

Object Changing Direction

Let’s Practice with Average Acceleration...

Sample Problem 2B Pg. 49 in your books.

Acceleration The slope and

shape of a graph plotting velocity vs. time describes the object’s acceleration.

When velocity on graph is

increasing : acceleration is positive

decreasing : acceleration is negative

constant : there is no acceleration

Velocity Vs. Time Graphs

Kinematic Formulas

Formulas in Textbook on Pg. 58

Section 3Falling Objects

Chapter 2 One Dimensional Motion

Free Fall Free fall is acceleration due to gravity.

Free fall acceleration is constant. Magnitude of free fall is 9.81 m/s2

Direction of free fall is directed downward. negative direction (-)

Free fall is denoted with the symbol g. (Sometimes may be ‘a’ for acceleration due to gravity)

Free Fall In a vacuum, in the absence of air resistance, all

objects fall at the same rate.

What goes up must come down. What causes an

object that has been thrown up into the air to come back down?

Free-Fall Acceleration due to gravity is always directed downward and pulling an object towards Earth’s surface.

Recall Information Remember we learned about a formula that can

be used to find final velocity at ANY displacement…

vf2 = vi

2 + 2aΔx (time is not needed)

We use this same formula but we change x to y

vf2 = vi

2 + 2aΔy

Guided Practice Open books to pg. 63 Sample Problem 2F