1. Chapter 2: Motion in One Dimension

2. Displacement Change in position of an object Frame of reference
A point against which position is measured
Example: A train traveling between stations
It is in motion when measured against the track.
It is stationary when measured against a seat.

3. Displacement Not equal to distance traveled Scalar vs. Vector
Distance vs. Displacement

4. Displacement (x)
Straight line distance from the initial position to the final position (change in position)
Can be positive or negative

5. Displacement (x) What is the displacement for the objects shown?
Answer: 70 cm
Answer: -60 cm

6. Displacement Sign Conventions
Uses a coordinate system
Right (or east) ---> +
Left (or west) ---> –
Up (or north) ----> +
Down (or south) ---> –

7. Speed vs.Velocity Scalar vs. Vector Distance vs. Displacement

8. Speed Speed does not include direction while velocity does.
Speed uses distance rather than displacement.
In a round trip, the average velocity is zero but the average speed is not zero.

9. Average Velocity = (ΔX/Δt) = displacement/time interval
Displacement in a given time
Average Velocity = (ΔX/Δt) = displacement/time interval

10. Average Velocity
How would you describe the motion shown by this graph?

11. Average Velocity Describe the motion of each object. Answers
Object 1: constant velocity to the right or upward
Object 2: constant velocity of zero (at rest)
Object 3: constant velocity to the left or downward

12. Instantaneous Velocity
Velocity at a single instant of time
Speedometers in cars measure instantaneous speed.
Determined by finding the slope at a single point (the slope of the tangent)

13. 0.98 m/s to the east Book Problems
Heather and Matt take a 34 minute walk eastward along a straight road to a store 2.0 km away. What is their average velocity in m/s?
0.98 m/s to the east
Book Problems

14. 3.47 m/s to the south Book Problems
Eugene is 75 km due south of Salem. If Joe rides from Salem to Eugene on his bike in 6.00 hr, what is his average velocity?
3.47 m/s to the south
Book Problems

15. 20.83 m/s to the south Book Problems
A bus traveled south along a straight path for 3.2 h with an average velocity of 88 km/h, stopped for 20.0 minutes, then traveled south for 2.8 h with an average velocity of 75 km/h. What is the average velocity for the total trip?
20.83 m/s to the south
Book Problems

16. 490,000 m to the south Book Problems
A bus traveled south along a straight path for 3.2 h with an average velocity of 88 km/h, stopped for 20.0 minutes, then traveled south for 2.8 h with an average velocity of 75 km/h. What is the displacement for the total trip?
490,000 m to the south
Book Problems