A 2 m × 1.5 m tank of 6 m height is provided with a 100 mm diameter orifice at the center of its base. The orifice is plugged and the tank is filled up to 5 m height. Consider the average value of discharge coefficient as 0.6 and acceleration due to gravity (g) as 10 m/s2. After unplugging the orifice, the time (in seconds) taken for the water level to drop from 5 m to 3.5 m under free discharge condition is ______________ (rounded off to 2 decimal places).
A rectangular channel is 4.0 m wide and carries a discharge of 2.0 m3/s with a depth of 0.4 m. The channel transitions to a maximum width contraction at a downstream location, without influencing the upstream flow conditions. The width (in meters) at the maximum contraction is ______________ (rounded off to 2 decimal places).
For a reconnaissance survey, it is necessary to obtain vertical aerial photographs of a terrain at an average scale of 1: 13000 using a camera. If the permissible flying height is assumed as 3000 m above a datum and the average terrain elevation is 1050 m above the datum, the required focal length (in mm) of the camera is
What is the CORRECT match between the survey instruments/parts of instruments shown in the table and the operations carried out with them?
| Instruments/Parts of instruments | Operations |
|---|---|
| P - Bubble tube | i - Tacheometry |
| Q - Plumb bob | ii - Minor movements |
| R - Tangent screw | iii - Centering |
| S - Stadia cross-wire | iv - Levelling |