Physics: Motion

 
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I can describe the relationship between the different aspects of motion (ie. speed, velocity, and acceleration).


Subskill:     I can explain the relationship between motion and a frame of reference.


Subskill:     I can differentiate between constant and changing motion of an object.


Subskill:     I can analyze and evaluate a graph which shows speed, velocity, or acceleration.


Subskill:     I can calculate time, distance, speed, velocity, and acceleration using algebra.


Subskill:     I can describe what happens to an object as its motion changes.

Learning Target

Acceleration

Formative Assignment #7
Due Date: Tuesday November 12th

1. Study the information presented on this page about acceleration.

2.    Complete the Acceleration Worksheet below
Cool Video

Usain Bolt

“The World’s Fastest Man”

100m Race
9.76 sec

Acceleration

In everyday English, the word acceleration is often used to describe a state of increasing speed.

For many Americans, their only experience with acceleration comes from car ads.

When a commercial shouts "zero to sixty in six point seven seconds" what they're saying here is that this particular car takes 6.7 s to reach a speed of 60 mph starting from a complete stop.

This example illustrates acceleration as it is commonly understood, but acceleration in physics is much more than just increasing speed.


Any change in the velocity of an object results in an acceleration: increasing speed (what people usually mean when they say acceleration), decreasing speed (also called deceleration or retardation), or changing direction.

Yes, that's right, a change in the direction of motion results in an acceleration even if the moving object neither sped up nor slowed down.

That's because acceleration depends on the change in velocity — one with both magnitude and direction.

Thus, a falling apple accelerates, a car stopping at a traffic light accelerates, and an orbiting planet accelerates.

Acceleration occurs anytime an object's speed increases, decreases, or changes direction.


Average acceleration is determined over a "long" time interval.

The word long in this context means finite — something with a beginning and an end.

The velocity at the beginning of this interval is called the initial velocity (v) and the velocity at the end is called the final velocity (v0).  Average acceleration is a quantity calculated from measurements.




The Physics Hypertextbook
© 1998–2010 Glenn Elert

Ticker Tape Diagrams

A common way of analyzing the motion of objects is to perform a ticker tape analysis.

A long tape is attached to a moving object and threaded through a device that places a tick upon the tape at regular intervals of time - say every 0.10 second. As the object moves, it drags the tape through the "ticker," thus leaving a trail of dots.

The trail of dots provides a history of the object's motion and therefore a representation of the object's motion.


The distance between dots on a ticker tape represents the object's position change during that time interval.

A large distance between dots indicates that the object was moving fast during that time interval.

A small distance between dots means the object was moving slow during that time interval.

Ticker tapes for a fast- and slow-moving object are depicted below.


The analysis of a ticker tape diagram will also reveal if the object is moving with a constant velocity or accelerating.

A changing distance between dots indicates a changing velocity and thus an acceleration.

A constant distance between dots represents a constant velocity and therefore no acceleration.

Ticker tapes for objects moving with a constant velocity and with an accelerated motion are shown below.


And so ticker tape diagrams provide one more means of representing various features of the motion of objects.

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