# ? Earth's Gravitational Field

#### samaank

???? Earth's Gravitational Field

Hi, i have a physics question in my physics portfolio, it goes as follows

Critically assess the following statement: ‘Astronauts in a space capsule orbiting the earth at a height of 900km experience weightlessness: hence the gravitational field due to the earth must be zero at that altitude'. Include calculations in your answer.

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#### russ_watters

Mentor
Have you tried the calculation?

#### samaank

i dont know what to calculate

#### ZapperZ

Staff Emeritus
2018 Award
samaank said:
Hi, i have a physics question in my physics portfolio, it goes as follows

Critically assess the following statement: ‘Astronauts in a space capsule orbiting the earth at a height of 900km experience weightlessness: hence the gravitational field due to the earth must be zero at that altitude'. Include calculations in your answer.

Think about this for a minute. If you are moving in a circular motion (which we will approximate the orbit to be), is there any acceleration on the capsule+astronauts system? If there is, there's a net force applied to that system. If there's no net force or acceleration, you'd have Newton's First Law. Is that what you have in this situation?

Once you figure that out, THEN you can start to try to explain why the astronauts experience weightlessness, which will lead to the conclusion that "weightlessness" does not mean zero gravitational force (example: astronauts training in the "vomit" plane).

Zz.

#### ZapperZ

Staff Emeritus
2018 Award
I just realized that you posted this in more than one location. Please do not do that! Spend some time reading our Guidelines before posting.

Zz.

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