1. Speed & Velocity
CMS
Georgia Davis

2. Speed Speed is the rate at which an object moves.
To calculate speed you must know the distance and time
The equation for speed is: speed = distance/ time or s = d/t
For example: a cyclist might travel 30 kilometers in 1 hour or 30km/h
We read the product as 30 kilometers “per” hour.

3. Suppose you walk 10 m down a hallway in 2. 5 s
Suppose you walk 10 m down a hallway in 2.5 s. What is your average speed?
Answer: 4m/s

4. Average Speed The speed of most moving objects is not constant.
To calculate average speed we use the equation: Average speed = total distance/ total time
Example:
Total distance = 32km + 13km
Total time = 2h + 1 h
Average speed = 45/3 = 15km/h

5. Graphing Speed Suppose you watched a dog walk beside a fence.
A graph can show the total distance walked in 10seconds.
The line will not be straight because dogs do not walk at a constant speed.

6. What is the average speed of the dog?

7. Velocity
Two birds leave the same tree at the same time. They both fly 10km/h for 5 min but do not end up in the same place. Why not?
They flew in different directions. Both had different velocities.
Velocity is speed plus direction.

8. Changing Velocity
Velocity changes when speed changes, direction changes, or both changes.
Situation
What Changes
Raindrop falling faster and faster
speed
Runner going around a turn on a track
Car taking an exit off a highway
speed & direction
Train arriving at a station
Car stopping at a traffic light
Baseball caught by catcher
Baseball hit by a batter
Why would it be important for an air traffic controller to know the velocities of incoming airplanes?

9. Acceleration Acceleration is the rate at which velocity changes.
Therefore an object accelerates if the speed (increase or decrease), direction, or both changes.

10. An increase in speed is referred to as positive acceleration.
A decrease in speed is referred to as negative acceleration or DECELERATION.
An object traveling at a constant speed accelerates if it changes direction.

11. Accelerating? Car traveling at constant speed of 65mi/h.
Runner rounding a turn.
Baseball pitched.
Stopping for school bus.
Swerving to miss a dog in road.
Riding the Ferris wheel at the county fair.

12. Calculating Acceleration
Acceleration = Final speed – Initial speed
Time
Speed’s unit is m/s & time’s unit is seconds.
Acceleration is change in speed/ time, therefore the unit is m/s/s or just m/s2
If the object is not changing direction, you can describe the rate at which its speed changes.

13. You try…
An airplane accelerates on a runway to 40m/s after 5seconds. What is the acceleration?

14. As a roller coaster car starts down a slope, its speed is 4m/s
As a roller coaster car starts down a slope, its speed is 4m/s. But 3 seconds later, at the bottom, its speed is 22 m/s. What is its average acceleration?
22m/s - 4m/s 3s
18/3 = 6m/s2

15. Slope =Rise/Run 4m/s 2s = 2m/s2

16. Fill in the graphic organizer for a car that starts from one stop sign and approaches the next stop sign. Use the following terms: velocity, positive acceleration, deceleration, and at rest.