Anonymous
Anonymous asked in Science & MathematicsPhysics · 4 months ago

# How is it that objects are 'used' to Earth's rotational momentum, but never get 'used' to other rotational momentum?

if i put a cup on the table, it stays there, despite the fact that it's moving at a tremendous rotational speed

but if you put a cup on a spinning playground ride, it will always fly toward the edge and fall off; it will never get used to the momentum

how is this?

Relevance
• 4 months ago

Is there gravity at the center of the merry-go round?

NO.

• 4 months ago

I am going to be silly for a moment. How do you KNOW that the object does NOT get used to a spinning merry go round?

What experiments have you done to confirm or otherwise your statement?

Put a steel mug onto the merry go round and determine the speed at which it falls off.

Now repeat the experiment by putting the mug on and increasing the rate of rotation but always keeping it substantially below the rate at which it span off.

Keep it spinning day and night for six months or so. Now determine the speed at which it flies off. I am certain that it will need a higher speed than that of the first experiment.

Does not that indicate that the steel mug DID get used to the motion of the merry go round, contradicting your claim?

Do the experiment yourself and then determine if I am telling the truth or not.

And if MY claim is correct then consider whether the REASON for the result is the one you indicate or not.

You cannot be an experimental physicist without making experiments. And you cannot be a theoretical physicist if your theories contradict experiment.

• Anonymous
4 months ago

The Earth is NOT moving at a tremendous rotational speed. It turns once in 24 hours, which is 0.0007 RPM.

• Anonymous
4 months ago

The effect mainly depends on *angular* velocity.

It takes the earth a whole day to rotate once. But a roundabout rotates in a few seconds. Huge difference.

• 4 months ago

There's the little matter of the magnitude of the centrifugal force. It's only 0.34% at the equator, and feels like a sight reduction of gravity. On a spinning playground ride, the force might be 10% of one gravity, or even more, and has a direction parallel to the ground.

The rotational speed of the cup on the table is actually really slow. Try standing in one spot, and rotating around at 1 degree every 4 minutes. That's how slowly the Earth spins.

• DW
Lv 6
4 months ago

The gravitational force pulling us and the cup on the table toward the center of the Earth is much stronger than the rotational momentum that would cause to move in a straight line and leave the planet's surface. So much stronger that we don't even notice the momentum.

For the cup on the playground ride, the friction holding it to the surface of the ride is weaker than its momentum and doesn't keep it attached to the surface.

It's not about getting "used to" anything. Physics doesn't work that way.

• Anonymous
4 months ago

That's because the coffee cup, the table, and the air around them are all moving at the same rotational speed. It's the difference that counts.

• Morningfox
Lv 7
4 months agoReport

No, that's not it. If the rotation rate was really fast, the cup would slip. Or you would have to tilt the table to stop the slip.

• Henry
Lv 5
4 months ago

Earth is probably flat and stationary with an angel at each corner.

• Steve4Physics
Lv 7
4 months agoReport

Well I thought it was funny, so have given you a thumbs-up to balance the 5 thumb-downs!