Which of the following statements is CORRECT with respect to 'Notch'/'Weir'?
1
A weir may be defined as an opening provided in the side of tank or vessel such that the liquid surface in tank is below the top edge of opening.
2
Notch is used in large structure.
3
Notch is used to measure small flow rate.
4
Weir is made up of made of metallic plates.