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# circular motion watch

1. a metre is approximately one ten millionth of the distance from the north pole to the equator. Assuming that earth is a sphere and that its axis of rotation is stationary calculate the speed of the building on the equator in m/s.

surely I do 10 million x 2 pi and then divide that by (60 x 60 x 24) but that gave me 727, the answer is apparently 463m/s

could someone help.

thanks
2. (Original post by bl64)
a metre is approximately one ten millionth of the distance from the north pole to the equator. Assuming that earth is a sphere and that its axis of rotation is stationary calculate the speed of the building on the equator in m/s.

surely I do 10 million x 2 pi and then divide that by (60 x 60 x 24) but that gave me 727, the answer is apparently 463m/s

could someone help.

thanks
Seemingly when the question gives the distance from the North Pole to the equator, it means the distance over the surface of the Earth, not the radius of the Earth.
3. (Original post by 16Characters....)
Seemingly when the question gives the distance from the North Pole to the equator, it means the distance over the surface of the Earth, not the radius of the Earth.
a sphere's surface area is 4 pi r2 though so if I divided 10 million by 4pi and square rooted it I would get an r of 892.06 which is way too small.

Am i misinterpreting what you are asking me to do
4. (Original post by bl64)
a sphere's surface area is 4 pi r2 though so if I divided 10 million by 4pi and square rooted it I would get an r of 892.06 which is way too small.

Am i misinterpreting what you are asking me to do
Yes, where did I mention surface area :-) The distance the question provides is the distance you would have to walk along the surface of the Earth to get from the North Pole to the Equator. i.e. imagine a piece of string in contact with the surface of the sphere going from pole to the Equator. It's a quarter of the circumference. (God this would be so much easier to explain with a diagram)
5. (Original post by bl64)
a metre is approximately one ten millionth of the distance from the north pole to the equator. Assuming that earth is a sphere and that its axis of rotation is stationary calculate the speed of the building on the equator in m/s.

surely I do 10 million x 2 pi and then divide that by (60 x 60 x 24) but that gave me 727, the answer is apparently 463m/s

could someone help.

thanks
Multiply 10 million by 4, that'll give the circumference
6. (Original post by 16Characters....)
Yes, where did I mention surface area :-) The distance the question provides is the distance you would have to walk along the surface of the Earth to get from the North Pole to the Equator. i.e. imagine a piece of string in contact with the surface of the sphere going from pole to the Equator. It's a quarter of the circumference. (God this would be so much easier to explain with a diagram)
I see thanks
7. (Original post by 16Characters....)
Yes, where did I mention surface area :-) The distance the question provides is the distance you would have to walk along the surface of the Earth to get from the North Pole to the Equator. i.e. imagine a piece of string in contact with the surface of the sphere going from pole to the Equator. It's a quarter of the circumference. (God this would be so much easier to explain with a diagram)
All those words, could've just said "they gave the distance you'd have to travel from the North Pole to some shack on the equator"

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8. (Original post by 16Characters....)
Yes, where did I mention surface area :-) The distance the question provides is the distance you would have to walk along the surface of the Earth to get from the North Pole to the Equator. i.e. imagine a piece of string in contact with the surface of the sphere going from pole to the Equator. It's a quarter of the circumference. (God this would be so much easier to explain with a diagram)
Imagination?

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