Why does something heavy dropping into a container sometimes make the container jump upwards?


I saw a TikTok of the contents of a huge can of refried beans all entering into a pot below the can at once, which caused the pot to jump upwards about half an inch. Why is that?

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The physics involved are explained by Newton’s third law.

For every action, there is an equal and opposite reaction. The statement means that the size of the forces created by the first object (the beans,) equals the size of the force on the second object (the pot.) The force, which is energy, is directly down on the pot. That energy has to go somewhere, it can’t go down so it bounces the pot up.

The object being dropped has downward momentum that momentum is transferred to the container, the container then applies that force to the surface where it was resting and “bounces” off the surface.

When the beans hit the pot they apply a downward force against it. This causes the pot to apply a downward force against the hard surface on which it’s resting. According to Newton’s laws, this causes the hard surface to apply an equal but opposite upward force on the pot. This is what causes the pot to jump.

All solid objects are flexible to a degree. So when the beans are dropped into the pot, the pot is deformed slightly and the forces inside the material of the pot cause it to spring back into its original form. This causes the pot to move back upwards and because of its momentum it bounces off the ground a little.