# Thought Of The Day_7_Gravity and Astronauts..!!

Note by Rohit Gupta
5 years, 4 months ago

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@Rohit Gupta sir,here is my answer-

Yes, there is gravity in the outer space.

Regarding the astronauts feeling weightless, anyone feels weightless till there is no reaction(to the action force) force provider, and in free space it is the case.There is no reaction provider against the force of gravity, hence they have an acceleration towards the force provider and don't feel their weight.(The parts of their rocket cannot be considered as normal reaction provider, as the whole system of rocket and it's parts, including the astronaut will be accelerating towards the planet)

Now, for the satellites, the case is very much similar to rotational motion(or even circular motion), they have a tangential velocity(perpendicular to gravitational force) and force of gravity as centripetal force, and since about the force provider(i.e. the planet) there is no torque(ignoring the force of gravity of other heavenly bodies, as they are much farther away) acting, the angular momentum of satellites about the planet remains conserved, and hence they keep on revolving around the planet at at a fixed rate(not exactly fixed, if we remove the ignored factors).

- 5 years, 1 month ago

Weightlessness is when, in frame of the person himself, the effective gravity appears to be zero..!!
case 1) there is no gravity at all
case 2) person is falling freely under gravity (As in the case of satellite and astronauts)!! The whole satellite is in free fall towards earth..!!

- 5 years, 4 months ago

No, there is no gravity in the artificial satellites. The gravity exists only on the surface of the Earth and not inside or outside the Earth.
The satellite revolves around the earth just because of the critical velocity. This can be calculated with the formula V = √((G×M)/R) ,Where G is the gravitational constant. M is the mass of the body being orbited (Earth). R is the distance from the center of the Earth to the object in orbit. Still require anything, please reply...ok

- 5 years, 4 months ago

If there is no gravity of earth near the satellite then what changes the direction of the velocity of satellite??

- 5 years, 4 months ago

Yes there is gravity.

With the gravitational pull they also experience a centrifugal force in opposite direction to gravitational force.

Also this pull is the one who provides centripetal alteration, which is necessary for revolving.

If I went wrong somewhere them plz correct me.

- 5 years, 4 months ago

Centrifugal force is just an imaginary force in frame of astronauts, how will you explain the case in a stationary frame attached to earth

- 5 years, 4 months ago

Although the Earth's gravity has a lesser effect on an astronaut orbiting the Earth in a spaceship than on a person on the surface of the Earth, this is not the reason why an astronaut experiences weightlessness.

The space shuttle, International Space Station and most other manned vehicles don't get that far from the Earth. The Earth's gravitational attraction at those altitudes is only about 11% less than it is at the Earth's surface.

If you had a ladder that could reach as high as the shuttle's orbit, your weight would be 11% less at the top. Put another way, a person who weighs 100 kg on the Earth's surface would weigh about 89 kg at the top of the ladder.

The reason why the person wouldn't feel weightless is because they are being pushed by the ladder - it is keeping them from falling.

If they were to jump off the ladder, then they would feel weightless, at least up until the time they splatted on the ground.

This is why astronauts feel weightless. The astronaut, the spaceship and everything inside it are falling towards the Earth.

The reason why the astronaut doesn't go splat is because the Earth is curved and the astronaut, the spaceship and everything inside it are moving 'sideways' fast enough that, as they fall towards the Earth, the surface of the Earth curves away from them.

They are always falling towards the Earth, but they never get there. . . . . .

Source

And sir, try solving Cool space question and Gravity weightlessness for interesting questions. . . . . $\huge\ddot\smile$

- 5 years, 4 months ago

Bravo..!! That is the correct reasoning..!!

- 5 years, 4 months ago

Yes sir, but that was not by me please see the source. Also I sorry for marking the wrong option in my question, the correct answer must be "The normal force is Zero", or atleast, that's the correct answer given in NSO paper, what's your say sir?

- 5 years, 4 months ago

yeah in that scenario normal reaction by chair has to be zero..!!

- 5 years, 4 months ago

Anyways, I've deleted that sir. . .

- 5 years, 4 months ago

Ok!!

- 5 years, 4 months ago

It seems that Sravanth has just copied all the answer and gave himself the credit

- 5 years, 4 months ago

Thanks! I've edited that. . .

- 5 years, 4 months ago

@Sravanth Chebrolu I didn't expect you to do this again.

- 5 years, 4 months ago

I'm sorry, I forgot that here, but you can see in the cool space question that I had mentioned the source, sorry again for my mistake.

- 5 years, 4 months ago

This answer is given by Steve Gagnon, Science Education Specialist . You can see the answer by clicking here.

- 5 years, 4 months ago

- 5 years, 4 months ago

No sir. Satellites revolve because there is no net torque acting on them therefore conserving their angular momentum. Once the rocket puts them into orbit it is done.

- 5 years, 4 months ago

@Rajdeep Dhingra yes you are right in saying that the angular momentum is conserved but the question was a little different.. y the astronauts feel weightlessness???

- 5 years, 4 months ago

ohh.. Sir I have misunderstood the question. Anyways sir I have asked U a doubt in a question (Balancing the ball). Please could U take the pain in seeing it sir.

- 5 years, 4 months ago

@Rajdeep Dhingra Replied !!!

- 5 years, 4 months ago

Thank You very much sir !

- 5 years, 4 months ago

Now I am waiting for your response there..!!

- 5 years, 4 months ago