Question

What force does earth's gravity exerts on a 81-kg astronaut who is orbiting in a space station at a distance from the SURFACE of the earth equal to 2 earth radii? Show your calculations.Your answer must be in newtons please help

Answer 1

somebody plz help i know its a physics question but i really need help with these physics questions

Answer 2

If he were on the surface of the earth, his weight would be 81g, approx 800N.

Since his distance is three times that and the force is in an inverse square relationship with the radius, divide by nine to get a force of about 89N.

Answer 3

so we would use the force of gravity equation ? sorry im completly clueless

Answer 4

Well, we know the acceleration of gravity at the earth's surface. We also know that gravitational attraction is an inverse square relationship. Combine these two facts to get the force at three times the radius. By the way, all my calculations are mental math approximations. If you want more decimal places of accuracy, use a calculator.

Answer 5

My calculator indicates about 88.2N, but I think three digit accuracy is suspect in this case. I think I would go with about 88N.

Answer 6

im confused i have to do all this without a teacher i dont have the undersstanding of all these terms i keep reading the book just not getting it :( i get whhat ur saying but im not clear

Answer 7

Look at it this way. We know the acceleration of gravity at the earth's surface is 9.8m/s^2. You know that, right?

Answer 8

yes i do

Answer 9

So, the weight at the earth's surface is 81(9.8) N. Still with me?

Answer 10

so you have to multiply the weight by the accelaration of gravity?

Answer 11

Yeah, force = mass times acceleration, right?

Answer 12

Actually, the weight is the force. You are given the mass (81 kg).

Answer 13

yeah but the astronaut is 81 kg tht is the weight no?

Answer 14

f=81(9.8)

Answer 15

No. It's the mass. The mass is the amount of "stuff" there. The weight is the force. How hard the mass pushes on the ground, which is proportional to the acceleration of gravity.

Answer 16

Now, from the gravitational equation, we know that the gravitational force is
\[F=\frac{m_1m_2G}{r^2}\]
Note that this is an inverse-square relationship with the radius.

Answer 17

and the radius is 2 right

Answer 18

We know that the final position of the astronaut is two earth radii above the surface, so his distance from the center is three earth radii. Since the radius has increased three times, and everything else is the same, the weight decreases by a factor of one ninth.

Answer 19

So our final calculation is 81(9.8)/9

I get about 88N.

Answer 20

Hope I was helpful. Do math every day.

Answer 21

i got 88.2 from all that we did
thank u so much i really appreciate it u really took the time to guide me step by step u were very helpful thank u so so much

Answer 22

also there a re a few more questions with this question i have my answers to them but i think they are too brief any help would be appreciated :)
the first question is .
as gravity is exerting a force on the astronaut why does the astronaut feel him or herself to be weightless?
i said because his net weight is zero and he is in a state of free fall making his weight zero
and the other question is can the astronaut tell the difference between the weightlessness she feels in orbit and the weightlessness she would feel if gravity werent acting on her? could you go anywhere you would not be affected by gravity explain
my answer is too the second part i said gravity is everywhere i know thats very short

Answer 23

When in freefall, the weight is whatever the force pulling toward the earth is. The apparent weight (observed by the astronaut) is zero in freefall, as you said. You are correct that you never escape gravity; you can get far enough away that the force is small, or get close to something else that has a larger pull at that point (think about being in orbit around the moon) but it never disappears. Do math every day.

Answer 24

thank u so much :)
im trying to do math