Let's break down your questions about the bird in the cages, focusing on the concepts of weight and forces involved. The scenarios you presented involve two different types of cages: a wire cage and a glass cage. Understanding how the bird's flight affects the weight experienced by the person handling the cage requires a look into physics, particularly the principles of forces and weight distribution.

Weight and Forces in a Wire Cage

When the bird is sitting on the floor of the wire cage, the total weight that the girl is handling is the combined weight of the bird and the cage itself. Now, when the bird starts to fly inside the cage, it exerts a downward force on the air inside the cage. This force is transmitted to the cage through the air, which means that the bird is still contributing to the total weight that the girl feels.

What Happens When the Bird Flies?

• The bird flaps its wings and generates lift.
• As it flies, it pushes down on the air, which in turn pushes down on the cage.
• The total weight experienced by the girl remains the same because the bird's weight is still acting on the cage through the air.

Thus, in the case of the wire cage, the girl will experience the same weight regardless of whether the bird is flying or sitting on the floor.

Weight and Forces in a Glass Cage

Now, let’s consider the glass cage. The same principles apply here. When the bird is sitting on the floor, the boy handling the cage feels the combined weight of the bird and the cage. When the bird starts to fly, it again exerts a downward force on the air inside the cage.

Understanding the Dynamics

• The bird generates lift by pushing down on the air.
• This downward force is transferred to the cage through the air.
• As a result, the boy also experiences the same total weight as before.

In both cases, whether it’s a wire cage or a glass cage, the weight experienced by the person handling the cage does not change when the bird flies. The air pressure and the forces at play ensure that the weight remains constant.

Comparing the Two Scenarios

The key difference between the wire and glass cages lies in their material properties, but this does not affect the weight experienced by the person handling them. Both cages are closed systems where the air pressure and forces are consistent, allowing the weight to remain unchanged regardless of the bird's activity.

Connection to the Moving Lift Case

This scenario is quite similar to a moving lift (elevator) case. When an elevator is moving up or down, the weight experienced by a person inside the elevator changes due to acceleration. However, if the elevator is moving at a constant speed (either up or down), the weight felt by the person remains the same. Similarly, in both cage scenarios, the weight felt by the handler remains constant because the bird's flight does not change the total force acting on the cage.

In summary, whether the bird is in a wire cage or a glass cage, the girl or boy handling it will experience the same weight, as the bird's flight does not alter the total weight due to the forces involved. This principle is a great illustration of how forces and weight interact in a closed system.