HardPhysicsfluid
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-- 8. A body starts from rest and moves for n seconds with uniform acceleration a. Its velocity after n seconds is v. The displacement of the body in last 4 seconds is:
A
4v/n
B
8v - 4v/n
C
4v/n * (n - 2)
D
8v/n
Explanation
v = an => a = v/n. Displacement in last 4s = S_n - S_{n-4} = 1/2 a n² - 1/2 a (n-4)² = 1/2 a [n² - (n² - 8n + 16)] = 1/2 a [8n - 16] = 4a(n - 2). Substituting a = v/n: S = 4(v/n)(n - 2).
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