A helium filled blimp will rise just so high into the atmosphere and then stop. Why? Will a smaller blimp rise higher than a larger one, if both are filled to the same pressure?

See explanation

Explanation:

When a helium blimp rises in the atmosphere, a point eventually comes when the buoyancy of the blimp compared to the air it displaces is no longer greater than gravity's pull on the blimp hence it stops rising.

A smaller blimp will rise more than a larger blimp at the same pressure because the weight of the blimp determines the altitude to which it will rise.