1. Motion, Speed, and Velocity
Physics
Motion, Speed, and Velocity

2. Standards Covered
Explain the relationship among distance, time, direction, and the velocity of an object
Use the formula v=d/t to solve problems related to average speed or velocity
Represent linear motion of objects on distance – time graphs

3. Motion When an object changes its position, motion has occurred.
Distance- How far an object has moved.
Displacement- How far an object has moved in relation to its starting point.
Consider direction
Example: Two runners travel along the same straight path in a straight line for 500 meters. At the end of the run their distances are the same but their displacements are different. How can this be so?

4. Reference Point
A place or object used to determine if an object is in motion or moving
Using trees on a moving train to determine train is moving

5. Measuring Distance
All systems of weights and measures, metric and non-metric, are linked through a network of international agreements supporting the International System of Units. The International System is called the SI
the meter for distance,
the kilogram for mass,
the second for time,
the ampere for electric current,
the kelvin for temperature,
the mole for amount of substance

6. Speed
S=D/T

7. Problems A bug crawled 25.0 cm in 5.0 seconds. Its
average speed was ______.
S=d/t
S= 25cm/5 sec
S= 5cm/sec
How far was a turtle able to travel In 2.5 seconds at speed of 25m/s?
D=ST

8. Speed- Distance an object travels per unit of time
Relationships between speed, distance, and time:
Speed = Distance/ Time = d/ t
Constant Speed- speed does not change over time
Average Speed- speed of motion when speed is changing
Avg Speed = Total Distance/ Total Time
Instantaneous Speed- speed at any given moment in time (speedometer)

9. Graphing Motion Graph distance on the y-axis and time on the x-axis
Slope = rise = distance = speed
run time

10. Distance - Time Graph
If something is not moving, a horizontal line is drawn.
If something starts out slowly and then speeds up, its change in speed can look like this.

11. Learning Checkpoint This graph shows several stages of motion:
Stage 1: 100 m in 10 s
Stage 2: 50 m in 10 s
Stage 3: 150 m in 20 s
Calculate the speed as indicated by each of the colors.
Calculate the average speed.
What is the total distance?
What is the displacement?

12. Solution Stage 1: S= d/ t 100 m/ 10 s= 10 m/s Stage 2: S= d/t
Ave Speed= Tot d/ Tot t
300 m/ 40 s= 7.5 m/s
Distance = 300 meters
Displacement = 0 meters

13. Velocity The speed and direction of an object’s motion.
88 km / hr southwest

14. Velocity Velocity is the rate of motion in a specific direction.
I'm going that-a-way at 30 kilometers per hour. My velocity is 30 kilometers per hour that-a-way.

15. Velocity
When velocity is changing, (change in speed, or direction) the word acceleration is used.
You speed up if the acceleration and velocity point in the same direction.
You slow down (also referred to as decelerating) if the acceleration and velocity point in opposite directions.

16. Velocity

17. Acceleration
Acceleration is a measure of how much the velocity of an object changes in a certain time.
Final Speed - Initial Speed
time

18. REVIEW: Does the term accelerating only mean "speeding up"?
No it refers to any change in speed or direction (velocity).
Examples:
· a car speeding up as it moves in the same direction
· a car slows down as its speed decreases
· a car changes the direction in which it is moving by some angle but speed does not change.