Things are rubbed against each other
Answer:

Explanation:
Let assume that the solid cylinder rolls down a frictionless incline. The translational speed can be found by using the Principle of Energy Conservation and the Work-Energy Theorem:


The translational speed is:



B. by taking measurements during an experiment
A hot air balloon rises in the first place because the air inside is hot, which rises. So, if the air inside is not heated, it fails to rise and falls. Warm air rises because the particles get excited and jiggle with the heat, and cause the air to take up more space. So, as the surrounding air is probably colder and denser, the less dense hot air rises up in the hot air balloon.