IB Physics HL A.3.12 Power Question Bank

Practise HL power calculations for wind turbines, energy dissipation, momentum flow, efficiency and system assumptions in exam questions.

Exam points

Analyse wind-turbine power using area, density, inlet/outlet speed and v³ scaling, including stated assumptions.
Calculate power from kinetic-energy rate, momentum flow, energy dissipation or electrical supply in HL systems.
Combine efficiency, force–speed and energy-rate relationships for turbines, vehicles, spacecraft and power plants.

[Maximum number: 2]

The graph shows the variation with time of the height of the International Space Station (ISS) during a 30-day period.

Figure for Question A.3.12—Power question 1 — IB Physics HL

The following data are available:

\begin{aligned} \text { Mass of Earth } & =5.98 \times 10^{24} \mathrm{~kg} \\ \text { Mass of the ISS } & =4.20 \times 10^{5} \mathrm{~kg} \\ \text { Radius of the Earth } & =6.38 \times 10^{6} \mathrm{~m} \end{aligned}

For the 30-day period indicated in the graph the loss of total energy of the ISS is $4.5 \times 10^{9} \mathrm{~J}$ .

Calculate the average rate at which the energy of the ISS is being dissipated.

$\begin{aligned} P=\frac{\Delta E}{\Delta t} \quad P=\text { « } \frac{-4.5 \times 10^{9}}{30 \times 24 \times 3600} \text { » }-1.7 \times 10^{3} W \end{aligned}$

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A.3.12—Power question 1