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Find the centripetal acceleration of the space shuttle

1. Suppose a space shuttle is in orbit 400 km from the Earth's surface, and circles the eart about once every 90 minutes. Find the centripetal acceleration of the space shuttle in its orbit. Express your answer in terms of g, the gravitational acceleration at the Earth's surface.

2. Ac=v2/r

3. I tried converting 400km/1.5 hr to km/h...then to m/s and divided by 90 min to find the centripetal acceleration, then divinding this answer by 9.8 to find the final answer in g's.

The answer is supposed to be .9 g's.

I have tried this probelm a million times, and I honestly think that my mistake is in converting 400km. I'm not sure though...
Last edited:


Homework Helper
You haven't used 400 km as the radius, have you? The radius is the distance to the center of the Earth, not to the surface. Recommend you show your actual calc if you need more help.

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