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Q2 : An object falling from rest in a vacuum near the surface of the Eath falls 16 feet during the first second , 48 feet during the second , 80 feet during the third second

How far will the object fall in t second ?

answer :

S16 = a1 + ( n-1 ) d

16 + ( 15 ) (32)

= 496

Okay, this is an arithmetic series so you can use that formula. But why are you taking n= 16? You were asked to find how far the object will fall in t seconds. Don't you think that will depend on t?