If Sunita enters an elevator wearing a balloon hat on a string, and the elevator starts descending rapidly, what happens to the balloon relative to Sunita, and why? Provide a very brief response.
The balloon will rise relative to Sunita. As the elevator descends rapidly, the acceleration of the elevator downwards is greater than the acceleration due to gravity acting on the balloon. Since the helium balloon is buoyant and less dense than air, it has a natural tendency to move in the opposite direction of acceleration. Therefore, while Sunita experiences a downward force, the helium balloon moves upwards, or appears to rise, because it is less affected by the elevator's rapid descent.