Figure 3 shows the basic principle of operation of a hand-operated salad spinner used to dry washed salads - AQA - A-Level Physics - Question 2 - 2017 - Paper 6

Given that gear C rotates four times for every one revolution of gear B, the torque on gear C cannot exceed the torque on gear B if there are no losses. The torque relationship can be described as:

$T_C = 4 \times T_B$

However, for the system to function within the limits of mechanical advantage, the power output cannot exceed the power input, hence the torque on gear C cannot be greater than on gear B.

The moment of inertia (I) can be calculated using the formula for torque:

$\tau = I \alpha$

Given:

• Torque on gear C (\tau) = 0.054 N m
• Angular acceleration (\alpha) can be found from angular speed: [ \alpha = \frac{\Delta \omega}{\Delta t} = \frac{76 , \text{rad s}^{-1}}{2.1 \text{s}} \approx 36.19 , \text{rad s}^{-2}] Thus:

Angular Impulse relates to the change of angular momentum and is defined by:

$J = \Delta L = I \cdot \Delta \omega$

where:

• J is the angular impulse
• \Delta L is the change in angular momentum
• I is the moment of inertia
• \Delta \omega is the change in angular velocity.

A large force applied quickly changes the angular velocity, resulting in a high angular impulse that can exceed the limits of the gear teeth. The rapid deceleration necessitates a greater input force, potentially leading to damage of the plastic gear teeth due to stress beyond the material's tolerance.