Question

Which of the following best explains, why a hot air balloon rises?

• A. The heating of the air causes the pressure inside the balloon to increase
• B. The cool outside air pushes the balloon higher
• C. The temperature difference between the inside and outside air causes convection currents
• D. Hot air has a lower density than cold air

Hint:

When considering buoyancy, remember that the object will rise in the fluid if it is less dense than the surrounding fluid.

Answer 1

The Correct Option is D

A hot air balloon rises because the hot air inside the balloon is less dense than the cooler air outside. According to Archimedes' principle, an object immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced by the object. In the case of a hot air balloon, the hot air inside the balloon is less dense than the surrounding cooler air, so it displaces a larger mass of cooler air, resulting in an upward buoyant force. This force is greater than the weight of the balloon, causing it to rise.

Hence, the correct answer is (d).