8/4/2019 Chapter 2 Notes -Motion Along a Straight Line

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AP Physics C Chapter 2 Notes

Alex George

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Chapter 2 Notes Motion Along a Straight Line

One-Dimensional Motion- The basic physics of motion where the object moves along a singleaxis.

Kinematics- The classification and comparison of motions. Motion is restricted in three ways: 1) the motion is along a straight line only. The line may be

vertical, horizontal, or slanted, but it must be straight. 2) Forces (pushes and pulls) cause

motion. 3) The moving object is either a particle, or it moves like a particle.

Position and Displacement

The position of an object is found in accordance to a reference point, often the origin (zeropoint) of the axis. The positive direction is the direction of increasing coordinates while the

opposite is the negative direction.

A change in position is called displacement. Displacement doesnt necessarily have to have a direction associated with it; a displacement

without direction is referred to as the magnitude of the displacement.

A Vector Quantity- is a quantity that has both a direction and a magnitude. In displacement, there are two features: 1) its magnitude is the distance between the final and

initial positions. 2) Its direction, from the original and final positions, can be represented by a

plus or minus sign if the motion is along a single axis.

Average Velocity and Average Speed

Average velocity- the ratio of the displacement that occursduring a particular time interval to that interval.

On a graph of position vs. time, the average velocity is the slope of the straight line thatconnects two points on the x (t) curve.

Average Speed- is a different way of describing how fast aparticle moves. The average speed requires the total distance

covered. Since the average speed does not include a direction, it is a scalar quantity.

Instantaneous Velocity and Speed

Instantaneous Velocity- how fast a particle is moving at agiven instant. The vis the rate at which positionxis

changing with time at a given instant; that is, vis the

derivative ofxwith respect to t. Also note that vat any instant is the slope of the positiontime

curve at the point representing that instant.

Speed- the magnitude of velociy tha is, speed is the velocity that has been sripped of anyinication of direction, eiether in words or via an algebraic sign.

8/4/2019 Chapter 2 Notes -Motion Along a Straight Line

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AP Physics C Chapter 2 Notes

Alex George

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Acceleration

When a particles velocity changes, the particle is said toundergo acceleration (or to accelerate). For motion along an

axis, the average acceleration over a time interval is shown by the equation to

the right. Where the particle has velocity at time and then velocity attime . Instantaneous acceleration is also shown to the right

A common unit of acceleration is the meter per second per second: or .

If the signs of the velocity and acceleration of a particle are thesame, the speed of the particle increases. If the signs are opposite,

the speed decreases.

Constant Acceleration: A Special Case

Assuming that acceleration is constant, the following equations areable to be derived:

Free-Fall Acceleration

Free fall Acceleration- it is represented by g. The acceleration is independent of the objectscharacterizes, such as mass, density, or shape; it is the same for all objects. The free fall

acceleration near Earths surface is a=-g=-9.8m/s2

and the magnitude of that acceleration is g =

9.8m/s2.

We refer the motion to the vertical yaxis with +y vertically up; we replace a withg, where g isthe magnitude of the free-call acceleration. Near Earths surface, g = 9.8 m/s

2(=32 ft/s

2)

Graphical Integration of Motion Analysis

FINISH AFTER LEARNING DERIVATIVES