DP Physics (last assessment 2024)
Question 18M.2.SL.TZ2.a.i
| Date | May 2018 | Marks available | [Maximum mark: 2] | Reference code | 18M.2.SL.TZ2.a.i |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Estimate | Question number | a.i | Adapted from | N/A |
a.i.
[Maximum mark: 2]
18M.2.SL.TZ2.a.i
In a pumped storage hydroelectric system, water is stored in a dam of depth 34 m.
The water leaving the upper lake descends a vertical distance of 110 m and turns the turbine of a generator before exiting into the lower lake.
Water flows out of the upper lake at a rate of 1.2 × 105 m3 per minute. The density of water is 1.0 × 103 kg m–3.
Estimate the specific energy of water in this storage system, giving an appropriate unit for your answer.
[2]
Markscheme
Average height = 127 «m»
Specific energy «= = 9.81 × 127» = 1.2 × 103 J kg–1
Unit is essential
Allow g = 10 gives 1.3 × 103 J kg–1
Allow ECF from 110 m
(1.1 × 103 J kg–1) or 144 m
(1.4 × 103 J kg–1)
[2 marks]
