One-Dimensional Kinematics Position, Distance, Displacement Average Speed/Velocity Acceleration.

One-Dimensional Kinematics

Position, Distance, DisplacementAverage Speed/Velocity

Acceleration

Online Tools/Announcements

• http:/aw-bc.com/walker/

• Online homework coming soon

• QUIZ over Chapter 2 one week from Thursday ( 9/6 )

• “Chapter Summary” may be useful for each chapter

2-1 Position, Distance, and Displacement

Before describing motion, you must set up a coordinate system – define an origin and a positive direction.

2-1 Position, Distance, and Displacement

The distance is the total length of travel ( m ); if you drive from your house to the grocery store and back, you have covered a distance of 8.6 mi.

2-1 Position, Distance, and DisplacementDisplacement is the change in position. If you drive from

your house to the grocery store and then to your friend’s house, your displacement is 2.1 mi and the distance you have traveled is 10.7 mi.

2-2 Average Speed and Velocity

The average speed is defined as the distance traveled divided by the time the trip took: Average speed = distance / elapsed time

2-2 Average Speed and Velocity

Average velocity = displacement / elapsed timeIf you return to your starting point, your average velocity is zero.

Conceptual Checkpoint 2-1

Conceptual Checkpoint 2-1

2-2 Average Speed and Velocity

Graphical Interpretation of Average VelocityThe same motion, plotted one-dimensionally and as an x-t graph:

2-4 Acceleration

Average acceleration:

(2-5)

This is for linear acceleration ( change in speed )For constant speed but change in direction: centripetal acceleration

2-4 Acceleration

Graphical Interpretation of Average and Instantaneous Acceleration:

2-4 Acceleration

Acceleration (increasing speed) and deceleration (decreasing speed) should not be confused with the directions of velocity and acceleration:

THURSDAY!!

• Go to lab stations as soon as you get to class

HOMEWORK ( show work )!!

• EVERYONE:• Pg 48 ( #s 4,10 ) Pg 49 ( # 14 ) Pg 50 ( # 32 )

• AP:• Pg 48 ( # 6 ) Pg 49 ( # 23 )

2-5 Motion with Constant Acceleration

If the acceleration is constant, the velocity changes linearly:

(2-7)

Average velocity:

2-5 Motion with Constant Acceleration

Average velocity:

(2-9)

Position as a function of time:

(2-10)

(2-11)

Velocity as a function of position:

(2-12)

2-5 Motion with Constant Acceleration

The relationship between position and time follows a characteristic curve.

2-6 Applications of the Equations of MotionHit the Brakes!

2-7 Freely Falling Objects

Free fall is the motion of an object subject only to the influence of gravity. The acceleration due to gravity is a constant, g.

2-7 Freely Falling Objects

An object falling in air is subject to air resistance (and therefore is not freely falling).

HOMEWORK!!

• Pg. 50 ( #44 )

• Pg. 51 ( # 49 )