Answer
$T=0.45s$
Work Step by Step
We know that;
$T=2\pi\sqrt\frac{m}{K}$..............eq(1)
Also,
$w=mg$
which can be rearranged as:
$m=\frac{w}{g}=\frac{5}{9.8}=0.51$ kg
We plug in the known values in eq(1) to obtain:
$T=2\pi\sqrt\frac{0.51}{100}$
$T=0.45s$
