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by marcosscriven 3828 days ago
I'm not sure if that's a question or a statement.Firstly, velocity and acceleration are different things. Velocity is change of distance with time (km/s), acceleration is change of velocity with time (km/s per second or km/s^2).

Secondly, an acceleration on a mass requires a force. Supposing there were an 'outward acceleration', where do you propose the 'outward force' is?
1 comments
1stop 3828 days ago
... We are talking a tangent on a circle that is changing every second.

So that is a change of velocity, which is acceleration. Outwards is clearly "out" of the circle. The tangent (on the curve) would be a snapshot of that "outward" velocity.

As a said: Tangential velocity is the same as saying outward acceleration. Unless you were referring to just that single "snapshot" in a frozen time scenario.

That "outward" force usually comes from a massive rocket... It is then maintained by the inward force of gravity.

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marcosscriven 3828 days ago
Nothing is accelerating outward. There's only one acceleration here, and that's towards the centre of the mass of Earth.
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1stop 3828 days ago
If that were the case then you could get into orbit by simply going straight up. Why do they go laterally up to 8km/s then? (if not to generate an 'outward' force?).

There are two vectors being added here. One is gravity. The other is a tangental/outward vector. When added together, they form an orbit. Ignore one, and you leave orbit, either by going into space, or smashing into earth. But there are clearly two forces/vectors. And one of them, is having it's direction changed by the other, and thus is acceleration... I don't know what other words I can use to describe it. But I fail to see where I'm wrong :\

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vectorjohn 3827 days ago
The only force, and therefore the only acceleration, when you're in orbit is the force of gravity. And therefore, the only acceleration is towards the center of Earth.

The thing in orbit is already moving with a high enough velocity that it isn't able to get closer to the Earth.

I guess maybe what you're saying, is if you take the velocity vector and apply the acceleration vector over time, that changes the velocity at the same rate as the curve of the Earth.

Either way, there is exactly one force vector (which causes exactly one acceleration vector), not two.

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marcosscriven 3827 days ago
Accidentally up voted you :)

They get to that vast 8km/s veloctiy you mention with huge rocket engines. Then they turn them off.

At that point the astronauts and their craft are in freefall.

You mention an outward 'vector'? You can only talk about forces and their effects on masses really. There's an intertia that resists the downward acceleration, but that's not a force.

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1stop 3827 days ago
Pretty sure inertia IS a force. But I think this point has been laboured enough.

Tomayto...Tomarto.

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marcosscriven 3827 days ago
A force is the product of mass and acceleration. Its SI units are kg.m/s^2

Inertia is an inherent property of mass. If it were the same as a force its units would be the same.

So it's really not tomayto...tomato I'm afraid. It's right and wrong.

You are right the point has been laboured, but it upsets me to think you would go on under this misconception.

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simbilou_ 3827 days ago
A laughable claim, mister Bond, perpetuated by overzealous teachers of science.
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marcosscriven 3827 days ago
:) https://www.explainxkcd.com/wiki/index.php/123:_Centrifugal_...
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