What holds a circularly-moving satellite in orbit while the force ...

[Frost2351]

What holds a circularly-moving satellite in orbit while the force of gravity pulls downward on it?
 
  What will be an ideal response?

Question 2

What is the period (in hours) of a satellite circling Mars 100 km above the planet's surface? The mass of Mars is 6.42  1023 kg, its radius is 3.40  106 m, and G = 6.67  10-11 N  m2/kg2.
 
  A) 1.75 h
  B) 1.25 h
  C) 1.15 h
  D) 1.00 h
  E) 1.45 h

[Juro]

Answer to Question 1

Answer: Nothing holds the satellite in orbit. It remains in orbit because the force of gravity pulls perpendicular to its motion, just as the speed of a bowling ball on a lane isn't changed by gravity. With no component of force in the direction of motion, no change in speed occurs. Only a change in direction occurs. The satellite has enough tangential speed to simply match Earth's curvature below.

Answer to Question 2

A

[Frost2351]

Excellent

[Joy Chen]

Wow, this really help