# Orbital Speed

Answer the following questions. Mark on the screen. You may change

#1 Suppose Jupiter Explorer I is cruising about the planet in a circular orbit with an orbital radius 4 times that of Explorer II. If Explorer IIās speed is v2, what is the speed of Explorer I?

a. 1/2 v2
b. v2
c. 2 v2
d. 4 v2
e. 16 v2
f. None of the above.

#2 The first artificial earth satellite, Sputnik I, fell back to earth because friction with the earthās atmosphere slowed it down. (All earth-orbiting satellites in low earth orbit are slowed at least a little bit by the same sort of friction.) As Sputnik I spiralled closer to the earth, its speed was observed to

a. decrease
b. remain the same
c. increase
#3 Suppose you want to send a 200 kg probe out of the solar system. If the probe is originally at the orbit of the Earth, what initial speed must it have in order to escape from the solar system? (Hint: ignore the gravitational pull by the Earth and any other planets the probe will encounter as it travels out of the solar system.)

a. 72.9 m/s
b. 29.7 km/s
c. 42.1 km/s
d. 617.6 km/s
e. four times T2
f. eight times T2