The period of a pendulum is independent of the mass of the bob so whether it's empty or filled with something, the period remains the same.

Answer:
1.12 m
0.08291 m
Explanation:
u = Upstream velocity = 0.4 m/s
Re = Reynold's number =
(turbulent)
= Viscosity of water = 
Here the flow is turbulent so we have the relation

The approximate location downstream from the leading edge where the boundary layer becomes turbulent is 1.4 m
Boundary layer thickness relation is given by

The boundary layer thickness is 0.08291 m
Answer is C. Because protons and neutrons are more massive then electrons so that means A and b and C are not right