1. Friday

2. What are we going to do?
Record data for 2 runs more than minimum block length
Conversions
Homework!
Review
Homework Handout #1
Motion Detectors

3. Main point
How to accurately describe the motion of objects

4. MPV’s
I will be recording data to see who has moved their car past the minimum distance twice
Get your papers out, complete all calculations
Task two job

5. Task 2 (Due Wednesday)
The results must by typed or printed on an index card (3x5 or 4x6) in a table that includes:
For each run: overall displacement/ distance/ time/ velocity
The correct unit value for each number
The mean of the 3 velocity times
Discuss at least 2 specific reasons why the values may not be absolutely correct (sources of error)
A drawing or photo of the car used to gather evidence is to be attached to the other side of the index card

6. Conversions
If you are converting to a smaller unit, multiply the measurement to get a bigger number.
If you are converting to a larger unit, divide the measurement to get a smaller number

7. Conversion Factors we use :
1 meter = 100 centimeters
1 meter = 1000 millimeters
1 kilometer = 1000 meters
Interchange meter for, seconds, grams, Newtons, Joules…

8. Time conversions 1 minute = 60 seconds 1 hour = 60 minutes
1 day = 24 hours
1 year = 365 days (approximation)

9. Example problem Convert 1.85 meters into centimeters
Since meters are larger than centimeters, we are converting to a smaller unit
We multiply by the converting factor (100) = 185 cm

10. Mathematically:
1.85 m x cm = cm m

11. Example, you try:
Convert 645 seconds into the same number of minutes

12. Answer Since we are converting to a larger unit, we divide by factor
645 sec / 60 = min

13. Another way to do the solution
Dividing is the same as multiplying by the inverse
645 / 60 = 645 x 1/60
645 sec x 1 min/ 60 sec = min

14. Try these 456.3 mm (millimeters) = _____ m 456.3 /1000 = .4563 m
8 days = ______ min
8 x (24) x (60) = min

15. Page 17 Write 550 millimeters as meters
Convert to bigger, divide
550/1000 = .550 m
Write 3.5 seconds as milliseconds
Convert to smaller, multiply
3.5 x 1000 = 3500 millseconds

16. Average velocity
Displacement / time
Units are m/s
V = d / t

17. Book Problems
Find the velocity in m/s of a swimmer who swims 110 m toward the shore in 72 s
Answer v = d/t = 110 m/ 72 s = 1.5 m/s

18. Problem 2
Find the velocity in m/s of a baseball thrown 38 m from third base to first base in 1.7s.
Answer v = d/t = 38 / 1.7 = 22 m/s

19. Problem 3
Calculate the displacement in meters a cyclist would travel in 5.00 h at an average velocity of 12.0 km/h to the southwest.
Answer:
Rearrange equation v = d/t to d = vt
D = vt = 12.0 km/h x 5.00 h = 60 km
Convert 60 km into meters
Convert to smaller units means multiply
60 km (1000 m/1 km) = 60,000 m

20. Manipulating equations
V = d / t
Vt = dt / t t’s cancel on right
Vt = d same as d = vt

21. Ex: problems
A) How long will it take you to travel a length 307 m at 6.4 m/s?
Ans: v = d/t = 307 /t t =307/6.4 = 48s
If a car travels 150 blocks in 34.3 seconds, what is it’s average velocity in m/s.
Ans: convert blocks to meters- 150 x .305 = 45.8m
Then calc. vel m /34.3s = 1.34 m/s

22. Try this
If you can go 30 meters in 2.0 second, what is your average velocity in m/s?
Answer: 30/2 = 15 m/s
What is your average velocity in km/h?
Ans: to convert to km, you divide 30 by 1000 = .03
to convert to hours, you divide 2 by 3600 =
Divide .03/ = 54.05

23. Or To convert from m/s to km/h multiply by 3.6
To convert from km/h to m/s divide by 3.6

24. Due Monday Homework Handout #1 You should get a copy from me in class
There is a copy on website

25. Motion Detectors
Gather much more information on motion during any given time period
Uses sound to measure position
Produces a visual report on motion information ( A graph)