Final answer:
The pressure on an object decreases as altitude increases, due to the decreased weight of air above. In a hot-air balloon, pressure differs at various altitudes, influencing ascent or descent. This is closely aligned with Bernoulli's principle where the pressure is inversely related to kinetic energy and altitude.
Step-by-step explanation:
The pressure on an object decreases with the increase in altitude from Earth's surface. As you go higher in altitude, the number of air molecules above you decreases, which means there's less weight exerting force on you, leading to lower atmospheric pressure. This is also illustrated by the Bernoulli's principle, which suggests that in conditions where a fluid's speed increases, usually near the top in the case of the atmosphere, the pressure within the fluid tends to decrease.
In the context of a hot-air balloon, the pressure of the gas inside the balloon can be different from the pressure of the surrounding atmosphere. More specifically, the hot air inside the balloon is at a higher pressure when at lower altitude due to heating, which causes the balloon to rise. Conversely, at higher altitudes, the pressure inside the balloon decreases with the decrease in external atmospheric pressure.
According to Bernoulli's equation, a fluid in a state of constant pressure which experiences an increase in kinetic energy per unit volume will see a corresponding decrease in potential energy per unit volume. Thus, the pressure is inversely related to the altitude when considering the Earth's atmosphere or a hot-air balloon's rise and fall.