A student investigates the rate of drainage of water from a vertical cylindrical tube with a drainage orifice at the bottom.
She fills the tube to a fixed height with water and measures the height of the water level every 10 seconds.
Describe a method she can use to investigate how the rate of drainage changes with the diameter of the drainage orifice.
The table below shows the results of one of her experiments using a 2 mm diameter orifice.
| Time (seconds) | Height of water (cm\text{cm}cm) |
|---|---|
| 0 | 60.0 |
| 10 | 48.0 |
| 20 | 38.5 |
| 30 | 30.8 |
| 40 | 24.6 |
| 50 | 19.7 |
| 60 | 15.8 |
Describe how the height of the water changes with time. Use data from the table to support your description.
The student repeats the experiment, but this time she uses a 4 mm diameter orifice. Suggest how the height-time curve for the 4 mm orifice would compare to the curve for the 2 mm orifice on a graph.
Suggest two ways the student could improve the investigation to make her results more reliable or precise.
Explain why the rate of drainage would be different if she used a much more viscous liquid (such as glycerol) instead of water, assuming the physical dimensions of the apparatus are identical.