Gravity question
Discussion
This will be simple for someone that has been to school more recently than me.
Whilst sitting in my armchair I am presumably acted on by a force of 1G. If the floor suddenly disappears I and the armchair will accelerate downwards at roughly 64ft per sec/per sec because of the 1G force.
So if I have a G sensor what will it read before and after the floor disappears.
I guess it will read 1G in both cases but in opposite directions.
Whilst sitting in my armchair I am presumably acted on by a force of 1G. If the floor suddenly disappears I and the armchair will accelerate downwards at roughly 64ft per sec/per sec because of the 1G force.
So if I have a G sensor what will it read before and after the floor disappears.
I guess it will read 1G in both cases but in opposite directions.
It depends on how the "G" sensor is setup/calibrated.
Dynamic G sensors are typically set up to offset the static gravity component. As such, they read zero G when stationary. This means they can be used to calculate things like vehicle dynamics in all 3 axis on earth. In effect they have a -1g offset in the vertical direction. This will therefore read zero g when you are sat on your chair, peak at 1g as you start to fall, and then return to zero g when you reach terminal velocity
Static G sensors are setup to read the Earths gravity, and so the Z axis will read 1g when sat on your chair, and will read zero g once you get to freefall.
Dynamic G sensors are typically set up to offset the static gravity component. As such, they read zero G when stationary. This means they can be used to calculate things like vehicle dynamics in all 3 axis on earth. In effect they have a -1g offset in the vertical direction. This will therefore read zero g when you are sat on your chair, peak at 1g as you start to fall, and then return to zero g when you reach terminal velocity
Static G sensors are setup to read the Earths gravity, and so the Z axis will read 1g when sat on your chair, and will read zero g once you get to freefall.
Eric Mc said:
If the floor disappears and you start to fall, the G mater will drop to Zero - as you are in free fall. As soon as you stop falling and come to rest, it will register 1G again.
Although he's be accelerating downwards, as you say I think it will read 0G and not negative. In other words, in a gravitational field you need to accelerate to maintain 0G whereas in space you can just float about...Edited by Simpo Two on Saturday 15th August 21:39
Eric Mc said:
What would it read if you are falling around the earth in earth orbit? It's EXACTLY the same as falling on earth.
Something in orbit is not accelerating - it is falling at constant speed - therefore it will read zero.A g-sensor measures acceleration, so reads positive on acceleration, zero at constant speed (or no speed) and negative on deceleration.
Is an object falling around the earth (i.e. in orbit) undergoing the same accelerative force as an object falling directly towards the ground?
Would a person in a spacecraft falling around the earth float in the spacecraft (i.e. experience Zero G)
Would a person in a spacecraft falling directly towards the ground also experience Zero G?
Would a person in a spacecraft falling around the earth float in the spacecraft (i.e. experience Zero G)
Would a person in a spacecraft falling directly towards the ground also experience Zero G?
Eric Mc said:
What would it read if you are falling around the earth in earth orbit? It's EXACTLY the same as falling on earth.
Falling is falling - whether you hit the ground or miss it.
0G, because you've got 1G keeping you in orbit vs. 1G acceleration away from Earth due to your tangential velocity. You are in equilibrium. Your rotational speed is keeping you up there and doing the same job as the floor. If you remove the rotational speed from the spaceship, you are no longer in equilibrium and accelerate towards earth at a rate approaching 1G.Falling is falling - whether you hit the ground or miss it.
If you're sitting on your chair on the second floor you aren't going anywhere because all forces are in equilibrium. No acceleration to measure. The G meter, which measures acceleration, not gravity, should, if it is to be of any use, tell you you are not accelerating. When the floor disappears you are no longer in equilibrium and accelerate downwards. Now, the G - meter should acknowledge your unfortunate predicament by confirming that you are accelerating downwards and are about to have a bad day.
Eric Mc said:
Will you be floating in your craft as you fall?
What will you, as the occupant, experience?
Acceleration towards the earth. Since I'm stiluck in a spaceship, I'll probably feel like I'm floating, but That's relative to the spaceship, not to Earth. Followed shortly by a sudden stop.What will you, as the occupant, experience?
If it reads 1G while you're sitting, what will it read when the floor vanishes? Now you're accelerating towards the earth's centre at 9.81m/s^2. which is acceleration due to gravity. 1G. It can't read 1G if that's what it said when you were sitting still, because your state of acceleration has changed. It can't say more than 1G, because you're accelerating due to gravity, the verydefinition of 1G. It can't now say 0G, because it's an accelerometer and I'm now accelerating directly towards the earth.
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