Chapter 20, Problem 62A

To determine

The weight of the displaced air.

Answer to Problem 62A

The weight of the displaced air is $20000\text{ N}$ .

Explanation of Solution

Given:

The total weight of the balloon including its load and the hot air in it is $20000\text{ N}$ .

Formula used.

The expression for buoyant force is,

  $F_{\text{Buoyant}}=\rho gV$

Here, $\rho$ is the density, $g$ is the acceleration due to gravity, and $V$ is the volume.

Calculation:

The hot-air balloon accelerating neither upward nor downward. Hence, the net force acting on the balloon is zero.

Consider the balloon is at rest.

Since the balloon is at rest, the buoyant force is equal to the weight of air displaced.

The weight of displaced air is,

  $\begin{array}{l}{F}_{\text{Buoyant}}=\text{Weight of air displaced}\\ \text{Weight of air displaced}=20000\text{ N}\end{array}$

Conclusion:

Thus, the weight of the displaced air is $20000\text{ N}$ .