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The question I'm having problem with follows: how long would one day have to be so that there would be weightlessness on the equator? (the teacher said that the correct anwser would be roughly 5 minutes)

Solving this by myself I couldn't reach any other conclusion than:

gravitational force = centrifugal force => mg=mvv/r => g=vv/r => vv=gr

(v-velocity of any point on the equator, r- radius of the Earth, 6,4 million meters)

which means that: v=7920m/s => T=2*pi*r/v=5077s=84 minutes

What did I leave out of the account?

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# Homework Help: Gravity and centrifugal force

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