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13.Oscillations
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$k$, $2k$, $4k$ અને $8k$....ધરાવતી સ્પ્રિંગને શ્રેણીમાં જોડતાં સમતુલ્ય બળ અચળાંક કેટલો થાય?
A
$2K$
B
$k$
C
$\frac{k}{2}$
D
$\frac{k}{4}$
Solution
(c) $\frac{1}{{{k_{eff}}}} = \frac{1}{k} + \frac{1}{{2\,k}} + \frac{1}{{4\,k}} + \frac{1}{{8\,k}} + ….$
$ = \frac{1}{k}\left[ {1 + \frac{1}{2} + \frac{1}{4} + \frac{1}{8} + …..} \right]$
$ = \frac{1}{k}\left( {\frac{1}{{1 – 1/2}}} \right)$
$ = \frac{2}{k}$ (By using sum of infinite geometrical progression $a + \frac{a}{r} + \frac{a}{{{r^2}}} + …\infty $ sum $(S)$ $ = \frac{a}{{1 – r}}$)
$\therefore {k_{eff}} = \frac{k}{2}.$
Standard 11
Physics
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