Practice Problems - 2

New questions (and answers below):

1.  Discuss each of Kepler's 3 laws.

2.  At what point in its orbit is the Earth closest to the Sun?

3.  At what point in its orbit is the Earth moving fastest?

4.  What causes seasons?

5.  What is a semi-major axis of orbit (a)?

6.  What is an Astronomical Unit (AU)?

7.  Consider Jupiter.  It's orbit is 5 AU in size (roughly).  How long should it take Jupiter to orbit the Sun once?  Show how this calculation would be done.

8.  What is the period of Earth's orbit around the Sun?

9.  What is the size of Earth's orbit (in AU)?

10.  A 10-kg object is pushed on by a 200-N force.  What will be the acceleration?

11.  What is the weight of a 100-kg man?

12.  Would the answer to 3 be different if he was on the moon?  How so?

13.  Consider yourself standing on a scale in an elevator.  The scale reads your weight.  Compared to being at rest, how would the scale reading change (if at all) if the elevator were:

A.  Moving with constant velocity upward
B.  moving with constant velocity downward
C.  Moving with constant acceleration upward
D.  Moving with constant acceleration downward
E.  If the cable snapped (yikes!) and the elevator were falling


>

1.  See notes.

2.  Perihelion, which is approximately January 3-4 each year.

3.  Same point as 3 above.

4.  Tilt of Earth's axis.

5.  Half the longest distance across the orbital path (ellipse).

6.  Defined as the semi-major axis of Earth's orbit - roughly 93,000,000 miles - or  half the longest width across Earth's orbit.

7.  5^3 = T^2

So, T = the square root of 125, or around 11 years.

8.  1 year, or approximately 365.25 days.

9.  Defined as 1 AU.  (About 93 million miles)

10.  F = m a

200 = 10 a

a = 20 m/s/s


11.  W = m g

W = 100 g = 980 newtons


12.  Yes.  The weight would be smaller (1/6 as much, since Moon surface gravity is 1/6 that of Earth).

13.  a.   your regular weight
b.  your regular weight
c.  greater than your regular weight
d.  less than your regular weight
e.  zero!  (meaning that you are "weightless")

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