A student investigates how the flexibility of a safety net affects the average force exerted on falling debris during an impact.

They set up an experiment in the lab where a steel sphere of mass $m$ is dropped vertically towards a suspended horizontal net, as shown in the diagram below.

Draw on this

Specifically, they compare two setups:

• Setup A: A stiff, high-tension wire mesh net.
• Setup B: A highly flexible, low-tension nylon mesh net.

The student releases the sphere from rest using an electromagnet at a fixed height $h$ above the light gate. Just before striking the net, the sphere passes through the light gate to measure its velocity. On contact with the net, the sphere is caught and brought to a complete stop at its lowest deflection point.

A digital millisecond timer connected to the light gate and sensors on the net records the exact duration of the deceleration (from first contact with the net to when it is momentarily brought to rest).

Explain how the student could carry out this investigation to compare the effect of the two nets on the average force exerted during the deceleration. Your explanation should include:

• How to determine the average force (suggesting key measurements and any necessary physical equations)
• How the benefit of the flexible safety net is demonstrated by the results
• Precautions and control variables needed to ensure accurate and valid results