1. Introduction to One-Dimensional Motion

2. What’s the difference between distance and displacement?
Distance: the total magnitude traveled
For example, if you have to take the long way around a traffic jam, your distance increases
Displacement: the shortest distance from the starting point to the ending point
Draw & label this picture on your notes

3. What is average speed?
Speed Is the distance an object travels per unit time

4. What is Average Velocity?
Average Velocity: The rate of change in displacement with respect to time
Velocity has both speed and direction
d= displacement
t = time
v = velocity (m/s) V

5. Units For Speed & Velocity
In science, we use the metric system and distance and displacement are measured in meters
Time is measured in seconds no matter what measurement system you are using
Therefore, speed & velocity are both measured in meters /second (m/s)

6. Speed & Velocity Examples
Speed is distance divided by time
2 cm/s
Velocity includes the direction
2 cm/s west
West

7. More Velocity Examples
If the runner goes around a 400m circular track 2 times, what is his displacement?
Straight line distance from beginning to end = zero
What is the distance covered?
2 times the circumference of the circle = 800m

8. Try these Speed/Velocity Problems #1 and #2
A car travels 1000 m in 50 s. What is the car’s speed?
Speed = distance/time = 1000 m/50 s = 20 m/s
A car travels 1000 m north in 50 s. What is the car’s velocity?
Velocity = displacement/time = 1000 m/50 s = 20 m/s, north

9. Sample Problem #3
A car travels 500 m east, 1000 m west and does it in 100s
What is the car’s average speed?
Speed= distance/time
= 1500 m/100 s
= 15 m/s
What is the car’s average velocity?
Velocity = displacement/time
= 500 m east/100 seconds
= 5 m/s, east

10. What is the difference between average velocity and instantaneous velocity?
Average Velocity: Total Displacement divided by total time
Instantaneous Speed/Velocity: Is speed or velocity at a certain moment
Ex: A school bus takes 200 seconds to travel 15 meters.
What is the average velocity?

11. Using Graphs to Calculate Speed

12. Practice Problems
A dog runs 15.3 m/s for 32 seconds. How far does he go?
How long does it take to go 12 m in a car travelling 28 m/s?
What is the speed of an airplane that flies 2000 km for 2.5 hours?

13. Practice Problems