When air is heated in a particular location, it expands and becomes less dense. This generates an upward (buoyant) force on the air, as it is lighter than an equal volume of unheated air.

When the air molecules compress, the volume of the straw decreases. This means the amount of displaced water decreases, as does the buoyant force. The straw, now more dense than the water ...

In this installment of Hot Science we present three questions that may help you to better understand buoyancy. The first is a kind of warm-up question, dealing with general buoyancy principles.

There are two forces acting on the life jacket - its weight and the force of the water pushing ... Things that float are buoyant. If the weight is greater than the upthrust, it sinks.