A density-gradient column is used to test a solid polymer sample. The sample is held fully immersed at a release position near the top of the column.
| Quantity | Value |
|---|---|
| volume of the sample | 2.0 × 10-5 m3 |
| weight of the sample | 0.27 N |
| liquid density at the release position | 1200 kg/m3 |
| liquid density at a lower position well above the base | 1500 kg/m3 |
| gravitational field strength, ggg | 10 N/kg |
Between the release position and the lower position, the liquid density increases continuously. The sample is rigid and remains fully immersed throughout this region.
Calculate the force that the liquid exerts upwards on the sample at the release position.
The sample is let go while it is at the release position.
Calculate the initial resultant force acting on the sample.
Give your answer as a magnitude and a direction.
Explain how the density gradient can produce an unsupported, stationary position for the sample before it reaches the base.
132 exam-style questions on Edexcel GCSE Physics 15.2 Pressure in fluids, covering 15.2.1 Atmospheric pressure and height, 15.2.2 Pressure in fluids, 15.2.3 Pressure, force and area, 15.2.4 Pressure and depth, 15.2.5 Pressure in liquids: depth and density, 15.2.6 Upthrust, and 15.2.7 Floating and sinking. Each one has a worked solution and a mark scheme showing where the marks go.