Notches vs. weirs: Evaluate the statement — “The notch is of bigger size and the weir is of a smaller size.” Choose the correct option.

Introduction:
Open-channel measurement uses notches (small openings in thin plates at tank edges) and weirs (barriers across full channels). Understanding their relative size and application is fundamental to flow measurement practice.

Given Data / Assumptions:

• The statement claims a notch is bigger and a weir is smaller.
• Standard definitions from hydraulics are used.

Concept / Approach:
A notch is a calibrated opening, generally of smaller size, fitted to the side of a tank or reservoir to measure relatively small discharges. A weir is a dam-like obstruction across an open channel, usually larger in scale, used to measure or control open-channel flow.

Step-by-Step Solution:
1) Recall definitions: notch = small opening in a plate; weir = barrier across channel width.2) Compare typical dimensions: notches are small; weirs span part or all of a channel.3) Therefore, the provided statement reversing their sizes is incorrect.

Verification / Alternative check:
Inspection of standard devices (rectangular/V-notch plates vs sharp-crested weirs in channels) confirms typical size relationships: notches are smaller apparatus; weirs are larger civil structures.

Why Other Options Are Wrong:

• Agree: Contradicts standard definitions and typical applications.
• Partly correct in rare cases: Misleading; device classification is not based on atypical installations.
• Cannot be decided without discharge: Device type and size convention are independent of discharge once the device is selected.

Common Pitfalls:

• Assuming “bigger discharge” automatically means “notch is bigger”. Device choice depends on site conditions and desired accuracy.
• Confusing V-notches with triangular weirs; the size convention still holds.

Final Answer:
Disagree