Eli5: An inertia demonstration experiment tells that: “A coin is placed on a smooth card which serves as a lid on a glass. When the card is pulled suddenly in the horizontal direction the coin falls into the glass.” But when we pull the card slowly and gradually, the coin will go with card. Why?

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Eli5: An inertia demonstration experiment tells that: “A coin is placed on a smooth card which serves as a lid on a glass. When the card is pulled suddenly in the horizontal direction the coin falls into the glass.” But when we pull the card slowly and gradually, the coin will go with card. Why?

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3 Answers

Anonymous 0 Comments

In the second example, the force applied to the card isn’t enough to overcome the friction between the card and the coin. In the first example, it is.

Anonymous 0 Comments

When the card is pulled slowly, the coin moves with it because of friction between the coin and the card. But there is a maximum amount of frictional force that can be applied before the coin will start to slip.

Force is equal to mass times acceleration, so the faster the card is accelerated, the greater the force that would have to be applied to the coin in order for the coin to move with it. If the card is pulled fast enough, this force becomes greater than what friction can apply and the coin will be left behind.

Anonymous 0 Comments

Real answer: Frictional transfer rate not being high enough to keep up. the coin *does* go with the card in both instances, it just slides off in the second example.

True answer: physics update times, if you move an object fast enough there’s clipping issues.