Q. A hydrogen-inflated polythene balloon is released from the surface of the earth. As the balloon rises to an altitude up in the atmosphere, what will happen to its shape and size? (UPSC Prelims 2003)
Answer: Increase in size
Notes: As a weather balloon rises into high altitudes, where air pressure decreases, the helium or hydrogen pressure inside the balloon increases and expands the balloon. This way the balloon and the radiosonde can rise at a consistent pace high into the atmosphere.