A liquid of density contained in a vertical U tube filled to a height h on each limb. It executes simple harmonic motion in its limbs when a small disturbance is given. Then the time period of its oscillation is
The restoring force responsible for oscillation is the weight of the liquid displaced. Hence using the condition for simple harmonic motion we can say that . Here . If the mass per unit length is , then and . Simplifying we get
Comparing this with we get
where . Hence the time period of oscillation is