If you wanted to make a profit buying gold by weight at one altitude and selling it at another altitude for the same price per weight, should you buy or sell at the higher altitude location?

1

• If you wanted to make a profit buying gold by
  weight at one altitude and selling it at another
  altitude for the same price per weight, should
  you buy or sell at the higher altitude location?

2
If you whirl a tin can on the end of a string and
the string suddenly breaks, the can will

• A. fly directly away from you
• B. fly directly towards you
• C. fly off, tangent to its circular path
• D. spiral away from your hand
• E. spiral in toward your hand

3
A car travels in a circle with constant speed.
The net force on the car

• A. is directed forward, in the direction of
  travel
• B. is directed toward the center of the curve
• C. is zero because the car is not accelerating
• D. none of the above

4
A car going around a curve is acted upon by a
centripetal force, F. If the speed of the car
were twice as great, the centripetal force
necessary to keep it moving in the same path
would be

• A. 4F
• B. F
• C. 2F
• D. ½ F

5
The shape of the path of the Earth about the Sun
is

• A. an ellipse with the sun at one focus
• B. a circle with the sun at the center
• C. an ellipse with the moon at one focus
• D. an ellipse with nothing at either focus

6
Keplers Laws
7
Johannes Kepler (1571-1630)
8
Keplers 1st Law

• The planets move in elliptical orbits with the
  sun at a focus.

9
Kepler

• Ellipses
• Equal areas in equal times
• Period, orbital radius of satellites

10
Keplers 3rd Law

• T2 / r3 ratio is the same for all satellites of
  an object

11
Astronomical Unit

• Average orbital radius from Earth to sun is 1 AU