An engineering student investigates the gravitational discharge of a heavy hydraulic fluid from a tall vertical column through a small circular orifice at its base.
The student records the height, hhh, of the fluid surface above the orifice at regular intervals of time, ttt. The experimental data is presented in the table below:
| Time, ttt (s\text{s}s) | Height, hhh (cm\text{cm}cm) |
|---|---|
| 0 | 120 |
| 15 | 92 |
| 30 | 69 |
| 45 | 50 |
| 60 | 34 |
| 75 | 21 |
| 90 | 11 |
State two measuring instruments the student would need to perform this experiment.
Plot a graph of height, hhh, against time, ttt, on a grid, and draw a curve of best fit.
Describe the relationship shown by your graph between the height of the fluid and time.
By considering density and hydrostatic pressure, suggest a physical explanation for why the fluid discharge rate decreases over time.