look at question 1 PHYSICS PAPER 3 2nd variant
How on earth do you measure the amplitude of oscillation

How could can CIE ask such a question when we have never done this before ?
What is the underlying concept ??
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The new pattern in PAPER 3 is to always ask something experimental.
SO please tell me a list of experiments/ experimental concepts that I should be aware of for BOTH paper 3 & 6