Extremely tiny bubbles may have a different power-law: speed linearly proportional to size.

Over small changes in temperature, if the right semiconductor is used, the resistance of the material is linearly proportional to the temperature.

I believe the magnetic moment would be linearly proportional to mass of the particle.

According to Hooke's law the magnitude of the force exerted by a spring is linearly proportional to its extension.

The fuel cell produces a voltage linearly proportional to the O partial pressure at the membrane.

The output signal of such a sensor is linearly proportional to the value or simple function of the measured property.

The number of individual impacts is linearly proportional to shot flow, exposure area, and exposure time.

Coverage is not linearly proportional because of the random nature of the process (chaos theory).

If these conditions are met, the magnitude of the sound is linearly proportional to the magnitude of the avoidance response.

In this case the stress is linearly proportional to the strain rate.