my thoughts on newton

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so, i used to have a beef with newton. i thought that an orbiting body should require the expenditure of anergy.

with the strong nonclear force i can understand not requiring energy,

there's no motion and therefore no change in velocity and therefore no acceleration and therefore no force.

but with an orbiting body there's change in velocity, a change in direction,

therefore force, and force should require the expenditure of energy.

but then i envisioned a pole with one end of rope tied to a pole and the other end tied to a rock,

if you put the rock "into orbit" around the pole, yes the rope is applying force, but i see no reason discounting friction it can't obit indefinitely.

clearly not all force requires energy expenditure.

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13 minutes ago, phillip1882 said:

clearly not all force requires energy expenditure.

That’s where the concept of work comes in. The salient variable is speed, not velocity. The force in circular motion is perpendicular to the motion, so no work is done. No change in kinetic energy; speed is constant.

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no its velocity, you can experience this with your car, when you turn your thrown to the side some. clearly force is being applied.

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48 minutes ago, phillip1882 said:

no its velocity, you can experience this with your car, when you turn your thrown to the side some. clearly force is being applied.

Kinetic energy depends on speed, not velocity.

A force is applied but it does no work, hence the speed is constant.

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1 hour ago, phillip1882 said:

no its velocity, you can experience this with your car, when you turn your thrown to the side some. clearly force is being applied.

You are still confusing force with expenditure of energy. A rock on the ground exerts a force on it but no energy is expended. Think about that.

To do work, i.e. to expend energy, there has to be motion in the direction of an applied force.  A weight falling through a distance can do work. But a stationary weight does not do any work.

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10 hours ago, phillip1882 said:

no its velocity, you can experience this with your car, when you turn your thrown to the side some. clearly force is being applied.

Do astronauts in the ISS feel themselves thrown to the side of the station?

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Do astronauts in the ISS feel themselves thrown to the side of the station?

no, but that's because gravity counter  acts the effect.

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You are still confusing force with expenditure of energy. A rock on the ground exerts a force on it but no energy is expended. Think about that.

yeah i understand, i was wrong, force doesn't necessarily require energy, but we should clearly indicate when force is being applied

Edited by phillip1882
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• 2 weeks later...

i also wanted to add, if you spin  the ship fast enough, you stick to the walls

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