When considering the scenarios of a bird flying inside different types of cages, we need to think about the forces at play and how they interact with the person handling the cage. Let's break this down step by step for both the wire and glass cages.

Understanding the Weight Experience

Scenario 1: The Wire Cage

In the case of the bird sitting on the floor of a wire cage and then suddenly flying, the girl handling the cage will actually experience a momentary increase in weight. Here’s why:

• When the bird is on the floor, its weight is supported by the cage, and the total weight felt by the girl is the combined weight of the cage and the bird.
• As the bird takes off and begins to fly, it exerts a downward force on the air inside the cage. According to Newton's third law, for every action, there is an equal and opposite reaction. This means that the air pushes down on the cage, and the cage pushes back up on the bird.
• During the flight, the girl will feel the weight of the bird as it is still exerting force on the air, which is in turn pushing down on the cage. Thus, she will feel a slight increase in weight until the bird settles back down.

Scenario 2: The Glass Cage

Now, let’s consider the glass cage. When the boy is handling the glass cage and the bird starts flying, the situation is quite similar:

• Initially, when the bird is resting on the floor, the boy feels the combined weight of the cage and the bird.
• As the bird takes off, it again exerts a downward force on the air inside the cage. The air pushes down on the cage, and the boy will feel a momentary increase in weight, just like in the wire cage scenario.

Comparing the Two Cases

Both scenarios result in a temporary increase in weight for the person handling the cage while the bird is flying. The key difference between the wire and glass cages lies in the material and structure:

• The wire cage allows for more airflow and visibility, while the glass cage is more enclosed and can create a different acoustic environment.
• However, in terms of physics, both cages behave similarly when it comes to the forces exerted by the bird flying inside them.

Relating to the Moving Lift Case

This situation can be compared to a moving lift (elevator) scenario. When an elevator accelerates upwards, the occupants feel heavier for a moment due to the additional force acting on them. Similarly, when the bird flies, the girl or boy feels a temporary increase in weight due to the forces at play. In both cases, the sensation of weight changes based on the forces acting on the system.

In summary, whether it's a wire or glass cage, the person handling it will experience a momentary increase in weight when the bird starts flying. This is due to the forces exerted by the bird on the air and the subsequent reaction felt by the handler. The analogy with a moving lift helps illustrate how forces can affect our perception of weight in different scenarios.