1. Earth’s Second Motion
Revolution!

2. Revolution Motion of one object around another.
Synonym for revolution, one word?
ORBIT!

3. Earth’s Period of Revolution
One year
About days (rotations)

4. So what’s up with that 0.25 of a day?

5. Not Exactly 0.25 days, though

6. Assignment
Calculate the orbital speed (assume circular orbit), of each planet (including Pluto) Show work. Answer in miles per hour. Use Table 21.1 on P 577 to help answer the following questions

7. Handout Questions to answer
 How long does it take Earth to orbit the sun once?
How many rotations occur during one orbit?
How long is one typical calendar year?
How long is a calendar leap year?
Why does a leap year exist? Explain
Calculate the orbit speed of each planet
Which planet revolves the fastest?
Which Planet revolves the slowest?
Study your data. Is there a pattern?

8. Table 21.1 on P 577

9. Sun
Radius or orbit (mi)
circ of orbit (mi)
years
Days
Hours
speed (mi/hr)
Mercury
36,000,000.00
226,194,671.06 88
2,112.00
107,099.75
Venus
67,000,000.00
420,973,415.58
225
5,400.00
77,958.04
Earth
93,000,000.00
584,336,233.57
365.25
8,766.00
66,659.39
Mars
142,000,000.00
892,212,313.62
687
16,488.00
54,112.83
Jupiter
483,000,000.00
3,034,778,503.37 12
105,192.00
28,849.90
Saturn
886,000,000.00
5,566,902,182.16
29.5
258,597.00
21,527.33
Uranus
1,783,000,000.00
11,202,919,402.70 84
736,344.00
15,214.25
Neptune
2,794,000,000.00
17,555,219,748.26
165
1,446,390.00
12,137.27
Pluto
3,666,000,000.00
23,034,157,336.12
248
2,173,968.00
10,595.44