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Rotational dynamics (A-level only)

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Question 4

An off-grid hybrid cargo hoist system at a mountain mining site uses a heavy flywheel to store energy and haul a loaded cargo skip up an incline.

  • The total mass of the loaded cargo skip is 8.50×103 kg8.50 \times 10^3 \text{ kg}8.50×103 kg.
  • The incline of the cable track is constant at 12.0∘12.0^\circ12.0∘ to the horizontal, and the length of the incline is 250 m250 \text{ m}250 m.
  • The total resistive force (friction and cable drag) opposing the motion is constant at 2.40 kN2.40 \text{ kN}2.40 kN.
  • The hoist's flywheel has a moment of inertia of 35.0 kg m235.0 \text{ kg m}^235.0 kg m2.
1.

Calculate the minimum angular speed of the flywheel at the start of the ascent so that the skip can complete the climb using only the energy stored in the flywheel. (Use g=9.81 m s−2g = 9.81 \text{ m s}^{-2}g=9.81 m s−2)

[5]
2.

When returning empty skips back down the incline, the hoist system operates in reverse. Suggest two advantages of keeping the flywheel connected to the cable drum during this downhill descent.

[2]
3.

The mining company plans to upgrade the system to support longer, steeper tracks. To do this, the flywheel system must be modified to store significantly more energy. Discuss design features of the flywheel that would maximize its energy storage capacity without increasing the overall mass of the hoist assembly.

[3]
Markscheme

Rotational dynamics (A-level only) Questions

  1. A Level
  2. /Physics
  3. /Rotational dynamics (A-level only)

8 exam-style questions on AQA A Level Physics Rotational dynamics (A-level only), covering Concept of moment of inertia (A-level only), Rotational kinetic energy (A-level only), Rotational motion (A-level only), Torque and angular acceleration (A-level only), Angular momentum (A-level only), and Work and power (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.

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