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Rotational dynamics (A-level only)

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1
Question 1

A hand-cranked honey extractor consists of a basket that spins inside a stationary outer container to extract honey from honeycombs. The principle of operation is as follows:

  • Handle A is attached to gear B, which rotates about a fixed pivot.
  • Gear B meshes with a smaller gear C, which is attached to the central axle of the rotating basket.
  • Gear C rotates at a greater angular speed than gear B.

A tangential force of 8.0 N is applied to handle A. Handle A is located at a radius of 45 mm from its centre of rotation.

1.

Calculate the input torque.

[2]
2.

Gear C rotates five times for every one revolution of gear B. Deduce whether it is possible for the torque on gear C to be greater than one-fifth of the input torque.

[3]
3.

It takes 3.2 s for the extractor basket to reach an angular speed of 48 rad s−148\text{ rad s}^{-1}48 rad s−1 from rest. The torque on gear C is a constant 0.060 N m during this time. Frictional losses are negligible. Calculate the moment of inertia of the basket about its axis of rotation.

[3]
4.

The gears are made of polymer (plastic). Explain, with reference to angular impulse, why a large force is exerted on the gear teeth if the user attempts to stop the loaded basket too quickly using the handle.

[3]

Rotational dynamics (A-level only) Questions

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