Chapter 2 Motion in One Dimension Section 1 Displacement 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

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 2 One Dimensional Motion

2-2 Acceleration  Acceleration measures the rate of change in velocity.  Has Magnitude & Direction.  SI Units : m/s 2  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 3 Falling 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/s 2  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… v f 2 = v i 2 + 2aΔx (time is not needed)  We use this same formula but we change x to y v f 2 = v i 2 + 2aΔy

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