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The earth has a radius of about 6400km. If an object could orbit the earth just at its surface, how fast would it have to travel?
the answer is 8km/s
1. I have no problem with the answer.
2. I get confused by the answer explanation :" Gravity provides the centripetal force that mains that orbit. If the centripetal force required is greater than gravity, the orbiting object moves away from the planet; if the centripetal forces required is less than the gravity, the object falls towards the planet."
. 3.According the formula :GMm/r^2=mg=mv^2/r. The direction should be the opposite:"If the centripetal force required is greater than gravity, the orbiting object falls towards the planet; if the centripetal forces required is less than the gravity, the object moves away from the planet."
4.thanks a lot.
the answer is 8km/s
1. I have no problem with the answer.
2. I get confused by the answer explanation :" Gravity provides the centripetal force that mains that orbit. If the centripetal force required is greater than gravity, the orbiting object moves away from the planet; if the centripetal forces required is less than the gravity, the object falls towards the planet."
. 3.According the formula :GMm/r^2=mg=mv^2/r. The direction should be the opposite:"If the centripetal force required is greater than gravity, the orbiting object falls towards the planet; if the centripetal forces required is less than the gravity, the object moves away from the planet."
4.thanks a lot.
