A rectangular block of mass m and area of cross-section A floats in a liquid of density . If it is given a small vertical displacement from equilibrium it undergoes oscillation with a time period T, then
- T 1 m
- T
- T 1 A
- T 1
Answer
(3) T 1 A
Solution
When the block is pushed down by a small distance y, the extra liquid displaced is Ay, so the extra upthrust acts as a restoring force
F = -(A g)y
F -y, the motion is SHM with force constant k = A g, hence
T = 2 mk = 2 mA g
T 1 A (also T m and T 1 )
Answer: (3)