5 (a) Which of these is a non-renewable source of energy? A geothermal B natural gas C tidal D solar (b) Explain why renewable sources provide an increasing fraction of the electricity supply for many countries - Edexcel - GCSE Physics Combined Science - Question 5 - 2018 - Paper 1

Renewable energy sources are becoming increasingly important due to their sustainability and environmental benefits. As countries aim to reduce greenhouse gas emissions and combat climate change, there is a significant shift towards harnessing energy from natural processes that are replenished constantly, such as solar, wind, and hydro power. Additionally, the declining cost of renewable technologies and increasing governmental incentives for clean energy adoption are contributing to their expansion in the electricity supply.

To find the minimum height, we use the formula for gravitational potential energy:
$PE = mgh$
where:
m = mass of water = 7.0 kg,
g = acceleration due to gravity ≈ 9.81 m/s², and
PE = kinetic energy gained = 1300 J.

Rearranging the formula gives us:
$h = \frac{PE}{mg}$
Substituting the values:
$h = \frac{1300}{7.0 \times 9.81} \approx 18.5 \, m$

Thus, the minimum height = 18.5 m.

To calculate the speed, we apply the kinetic energy formula:
$KE = \frac{1}{2}mv^2$
where:
KE = kinetic energy = 1100 J,
m = mass of water = 8.0 kg.

Rearranging for speed yields:
v = \sqrt{\frac{2 \times KE}{m}}
Substituting the values:
v = \sqrt{\frac{2 \times 1100}{8}} \approx 17 , m/s.

Thus, the speed = 17 m/s.

From the graph, the kinetic energy of moving air at 15 m/s is approximately 5.2 kJ, while at 13 m/s it is approximately 3.9 kJ.
The energy transferred to the turbine can be calculated as:
$\text{Energy Transferred} = 5.2 \, kJ - 3.9 \, kJ = 1.3 \, kJ.$

To find the percentage of kinetic energy transferred: