Question 17N.3.HL.TZ0.11b
| Date | November 2017 | Marks available | [Maximum mark: 2] | Reference code | 17N.3.HL.TZ0.11b |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Estimate | Question number | b | Adapted from | N/A |
The diagram shows a simplified model of a Galilean thermometer. The thermometer consists of a sealed glass cylinder that contains ethanol, together with glass spheres. The spheres are filled with different volumes of coloured water. The mass of the glass can be neglected as well as any expansion of the glass through the temperature range experienced. Spheres have tags to identify the temperature. The mass of the tags can be neglected in all calculations.
Each sphere has a radius of 3.0 cm and the spheres, due to the different volumes of water in them, are of varying densities. As the temperature of the ethanol changes the individual spheres rise or fall, depending on their densities, compared with that of the ethanol.
The room temperature slightly increases from 25 °C, causing the buoyancy force to decrease. For this change in temperature, the ethanol density decreases from 785.20 kg m–3 to 785.16 kg m–3. The average viscosity of ethanol over the temperature range covered by the thermometer is 0.0011 Pa s. Estimate the steady velocity at which the 25 °C sphere falls.
[2]
use of drag force to obtain r3 x 0.04 x g = 6 x x 0.0011 x r x v
v = 0.071 «ms–1»
