1. Describing and Measuring MOTION
Section 1.1 Notes

2. Key Concepts When is an object in motion?
How do you know an object’s speed and velocity?
How can you graph motion?

3. Describing Motion
You are in MOTION if your distance from another object is changing
Depends on a REFERENCE POINT
Place or object used for comparison

4. Describing Motion Are you moving?
Reference point = SMARTboard
Ref. pt. = Sun
To determine motion, you must know your reference point!!

5. Relative Motion Motion is relative to your reference point. Questions:
On the next slide, are the skydivers moving relative to each other?
Are they moving relative to the airplane from which they jumped?
Are they moving relative to the ground?

6. Relative Motion Boat example: people in boat compared to shore – why?
people in boat compared to boat – why?

7. Measuring Distance You use units of measurement to describe motion
SI System is used to describe the distance an object moves.
Meter – basic measurement for length

8. Review: How many cm in a m? 100 centimeters in a meter
How many mm in a m?
1000 millimeters in a meter
How many m in a km?
1000 meters in a kilometer

9. Converting Units Practice Problem
- Describing and Measuring Motion
Converting Units
Practice Problem
How many centimeters are in 22.5 meters?
HINT = Multiply length by 100.
22.5 m = 2,250 cm

10. SPEED The distance an object moves in a certain amount of time
Speed = distance / time
Units depend on measures of distance and time
m/s km/h m/h

11. Average Speed Overall speed of an object
Calculate by dividing total distance by total time

12. Instantaneous Speed
Rate at which an object is moving at a given instant in time.
Why is the
instantaneous speed
different from the
average speed?

13. Question: Would a radar gun (used by police officers) measure
average speed or
instantaneous speed?
WHY?
Answer: Instantaneous speed

14. VELOCITY Speed in a given direction.
You need to know the direction to know velocity
Important to: pilots, weather forecasters, air traffic controllers

15. Graphing motion!! Motion graphs plot distance versus time
Slope = rise/run
Slope = distance/time
Slope = speed of that segment

16. Graphing Motion

17. Converting Units - Describing and Measuring Motion
Use a conversion factor to convert one metric unit to another. A conversion factor is a fraction in which the numerator and denominator represent equal amounts in different units. Multiply the number you want to convert by the conversion factor.
Suppose you want to know how many millimeters (mm) are in 15.5 meters (m). Since there are 1,000 millimeters in 1 meter, the conversion factor is:
1,000 mm/1 m
Multiply 14.5 meters by the conversion factor to find millimeters.
14.5 m X 1,000 mm/1 m
= 14.5 X 1,000 mm
= 14,500 mm

19. Graphing Motion Activity
- Describing and Measuring Motion
Graphing Motion Activity
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