checkout www. physicsclassroom.com

Speed and Velocity

Vectors are represented by arrows.

• the head of the arrow points in the direction of motion.• the length of the arrow is proportional to the magnitude of the vector.

This vector has the largest magnitude.

This vector has the smallest magnitude.

Adding and Subtracting Vectors in

1 Dimension using Diagrams

studyphysics.ca

A B

A + B

A B

A - B

A + (-B)

Distance - a scalar quantity. - "how much ground an object has covered" during its motion. - additive total of all the displacements

Displacement - a vector quantity. -"how far out of place an object is" - the object's overall change in position.

6 m

6 m

3 m3 m

Speed -is a scalar quantity. - refers to "how fast an object is moving." -speed is the rate at which an object covers distance.

Velocity -is a vector quantity. - refers to "the rate at which an object changes its position."

Average Speed Distance TraveledTime of Travel

=

Average Velocity Δ positiontime

= = displacementtime

Example 1:

A runner wins a 1.00 x 102 m race in 10.54 seconds. Find the average speeds in m/s and km/hr.

(Don't round off yet!)

Notice that the answer is slightly different when you use the rounded number.

(Always write down your formula!)

(Show our substitutions. Always include the units.)

Example 2

A cat starts at zero and walks 25 m west in 5 s and then moves 33 m east in 10 seconds. Find the average speed the cat travelled.

(Don't round off yet!)

(Don't round off yet!)

(Don't round off yet!)

Now you can round your answer off

(t1 and t2 are time intervals and not clock readings so I add them together to get the total time )

To find the displacement we must first find the final position

Example 3

A cat starts at zero and walks 25 m west in 5 s and then moves 33 m east in 10 seconds. Now find the average velocity the cat travelled.

The slope of the position vs time graph gives you the average velocity when the particle is moving at a constant velocity.

Determine the average velocities for the following situations

5

5

Blue Book pages 8-13

Yellow Book questons 7-9 pages 4 and 5