Orbital Velocity Interactive (107.0K)
Do all bodies orbiting at Earth’s distance from the Sun move at the same speed? How would Earth’s orbital velocity differ if the Sun were more or less massive? Is Earth’s velocity greater or smaller than Mars? This Interactive will answer those questions, and make it clear that the orbital velocity of any world depends on only two things: its distance from its star, and the mass of that star.

1		Earth's 1 g applies only at or near the Earth's surface. LEO satellites are usually only 200-300 miles high, close enough that the 18,000 mph velocity still works well. Given the Earth has a circumference of 25,000 miles, what is the approximate period of LEO satellites like the International Space Station, Hubble Space Telescope, and the Shuttle? Need a Hint?
			A)	About 16 minutes.
			B)	An hour.
			C)	About ninety minutes.
			D)	24 hours.

Given that the mass of the body plays a major role in determining orbital velocity, lets apply it to other bodies such as our Moon.

2		Given the Moon's surface gravity is only 1/6 g, what would the orbital speed of the Apollo Command/Service Module have been, just above the lunar surface, waiting for the return of the astronauts on the lunar surface? Need a Hint?
			A)	1,500 mph.
			B)	3,000 mph.
			C)	6,000 mph.
			D)	25,000 mph.

Newton visualized a huge cannon atop the highest mountain sending a cannonball at 18,000 mph in a constant free fall that matched the curvature of the Earth. Of course, we now know that air resistance means we must get up much higher than Everest with multistage rockets to reach orbital velocity, but it has great application in our study of satellites above us in LEO (low earth orbit), the geosynchoronous communication satellites so vital to the Internet, and the satellites around other planets, and even planets around other stars and star systems.

3		The satellites in geosynchronous orbit have a period of 24 hours, to stay hovering above the same place on Earth. Apply the orbital velocity formula to find their speed, given that 22,000 miles altitude is about 6.5 Earth radii. Need a Hint?
			A)	2,500 mph
			B)	7,000 mph
			C)	12,000 mph
			D)	25,000 mph

The satellites around other planets move at different speeds, depending on their distance from their planet and the mass of their home world.

4		If Io orbits 2.5x closer to Jupiter than does Ganymede, how do their orbital velocities compare? Need a Hint?
			A)	1.6 times faster.
			B)	2.5X faster.
			C)	6.25X faster
			D)	the same speed as Ganymede.

Even planets around other stars and star systems can have their orbital velocities calculated with this powerful formula.

5		The closest known planet to Nu Andromeda orbits its star in only 4.6 days; from its spectrum, we estimate the star is about four times more massive than Earth. If its is orbiting only .06 AU from its star, how much faster must this planet be moving, compared to Earth's orbital velocity of 30 km/sec? Need a Hint?
			A)	24 X faster
			B)	8 X faster
			C)	6 X faster
			D)	2.5 X faster