A student investigates the rate at which water drains from a cylindrical container to model how pressure affects flow rate.
She places a vertical cylinder with a small drainage hole at the bottom on a level bench and measures the height of the water column inside the cylinder every ten seconds. She wants to investigate how the rate of draining changes with the diameter of the drainage hole.
Describe a method she can use to carry out this investigation.
The table below shows the results from one of her trials using a 2 mm diameter hole:
| Time (seconds) | Height of water (cm\text{cm}cm) |
|---|---|
| 0 | 50.0 |
| 10 | 41.5 |
| 20 | 34.0 |
| 30 | 27.5 |
| 40 | 22.0 |
| 50 | 17.5 |
Describe how the height of the water changes with time. Use data from the table to support your description.
If the experiment is repeated with a hole of 4 mm diameter, with everything else remaining the same, describe how this new height-time curve would compare to the 2 mm curve.
Suggest one way to improve the investigation to get more reliable or accurate measurements.
Explain why using a liquid with a much higher viscosity, such as glycerol, instead of water (with the same apparatus and hole diameter) would affect the rate of draining.