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13.Oscillations
easy
A simple pendulum of length $ l$ has a brass bob attached at its lower end. Its period is $T$. If a steel bob of same size, having density $ x$ times that of brass, replaces the brass bob and its length is changed so that period becomes $2T$, then new length is
A
$2 l$
B
$4 l$
C
$4 l x$
D
$\frac{{4l}}{x}$
Solution
(b) $T \propto \sqrt l $ Time period depends only on effective length. Density has no effect on time period. If length made $4$ times then time period becomes $2$ times.
Standard 11
Physics