Bird in Spring Balance – Rankers Physics

Third Law of Motion: Practice Problem & Solution

Assertion (A): An air tight cage in which a bird is sitting, is suspended from a spring balance. If the bird starts flying upwards with some acceleration, then the reading of the balance will increase. Reason (R): The weighing machine measures the actual weight of a body.  
(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(3) (A) is true but (R) is false
(4) Both (A) and (R) are false

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Third Law of Motion. Understanding the underlying formula is key to arriving at the correct answer below:

When the bird flies up with acceleration, it pushes more air downwards, increasing the effective weight measured. So (A) is true. A weighing machine measures apparent weight, not always actual weight. Thus (R) is false.

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