Lecture Outlines Chapter 2

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2007 Pearson Prentice Hall

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Lecture Outlines

Chapter 2

Physics, 3rd Edition

James S. Walker


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Chapter 2

One-Dimensional Kinematics


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Units of Chapter 2

Position, Distance, and Displacement

Average Speed and Velocity

Instantaneous Velocity

Acceleration

Motion with Constant Acceleration

Applications of the Equations of Motion

Freely Falling Objects


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2-1 Position, Distance, and Displacement

Before describing motion, you must set up acoordinate system define an origin and a positive

direction.


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The distance is the total length of travel; if you drive

from your house to the grocery store and back, you

have covered a distance of 8.6 mi.


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Displacement is the change in position. If you drive

from your house to the grocery store and then to

your friends house, your displacement is 2.1 mi and

the distance you have traveled is 10.7 mi.


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2-2 Average Speed and Velocity

The average speed is defined as the distancetraveled divided by the time the trip took:

Average speed = distance / elapsed time

Is the average speed of the red car 40.0 mi/h, morethan 40.0 mi/h, or less than 40.0 mi/h?


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Average velocity = displacement / elapsed time

If you return to your starting point, your average

velocity is zero.


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Graphical Interpretation of Average Velocity

The same motion, plotted one-dimensionally

and as anx-tgraph:


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2-3 Instantaneous Velocity

Definition:

(2-4)

This means that we evaluate the average velocity

over a shorter and shorter period of time; as that

time becomes infinitesimally small, we have the

instantaneous velocity.


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2-3 Instantaneous Velocity

This plot shows the average velocity being

measured over shorter and shorter intervals. The

instantaneous velocity is tangent to the curve.


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2-4 Acceleration

Average acceleration:

(2-5)


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2-4 Acceleration

Graphical Interpretation of Average and

Instantaneous Acceleration:


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2-4 Acceleration

Acceleration (increasing speed) and deceleration

(decreasing speed) should not be confused with thedirections of velocity and acceleration:


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2-5 Motion with Constant Acceleration

If the acceleration is constant, the velocity changes

linearly:

(2-7)

Average velocity:


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Average velocity:

(2-9)

Position as a function of time:

(2-10)

(2-11)

Velocity as a function of position:

(2-12)


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2-6 Applications of the Equations of Motion

Hit the Brakes!


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2-7 Freely Falling Objects

Free fall is the motion of an object subject only to

the influence of gravity. The acceleration due togravity is a constant, g.

2 F l F lli Obj


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An object falling in air is subject to air resistance

(and therefore is not freely falling).

2 7 F l F lli Obj t


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Free fall from rest:

2 7 F l F lli Obj t


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Trajectory of a projectile:

S f Ch t 2


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Summary of Chapter 2

Distance: total length of travel

Displacement: change in position

Average speed: distance / time

Average velocity: displacement / time

Instantaneous velocity: average velocity measured

over an infinitesimally small time

S f Ch t 2


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Summary of Chapter 2

Instantaneous acceleration: average acceleration

measured over an infinitesimally small time

Average acceleration: change in velocity divided

by change in time

Deceleration: velocity and acceleration haveopposite signs

Constant acceleration: equations of motion relate

position, velocity, acceleration, and time

Freely falling objects: constant acceleration

g= 9.81 m/s2

Lecture Outlines Chapter 2

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