Question

A parrot is sitting on the floor of a wire cage which is being carried by a boy, starts flying. The boy will feel that the box is now.
(A) Heavier
(B) Lighter
(C) Shows no change in weight
(D) Lighter in the beginning and heavier

Answer 1

Hint: In an airtight container, when the bird is sitting inside a container, now the weight of the container is the sum of the weight of the container and the bird. Now here, we know that this is in a wire cage so the air escapes through the holes. So, the boy can feel only the weight of the cage.

Completer answer:
When the parrot is sitting on the cage, a boy can carry the weight of the parrot and cage.
We know that the bird starts flying in the cage, which means now the bird is now in the air. In a closed space, if the bird can fly the weight of the birds pushing downwards the cage and the weight of the cage are increasing. But from the question, we know that the bird is in the wire cage. In the wire cage, there are a lot of holes so the air can escape easily. So here, the air is not deep in the cage. So now, the bird is only in the air.
By the newton's third law of motion, when the bird starts flying inside the cage, there is no weight inside the floor of the wire cage, so that the boy will experience light weight in the wire cage. Hence, the weight of the bird doesn't act in the wire cage because all the air escapes to the atmosphere but in the closed space the air doesn’t escape. So, there is weight is increasing but here, the air escapes. So, the only the weight of the cage only a boy can feel now.
Thus, now the weight of the cage is lighter.

Therefore, option (B) is correct.

Note: From the question, we know that the bird is in the wire cage, in the wire cage there are a lot of air holes. If the bird is flying inside the cage, the weight of the birds doesn't act on the cage and the air is split over the cage. Air escapes through the holes.