A rail inspection trolley of mass 450 kg travels at 6.0 m/s. Engineers test two types of end stop. Each end stop brings the trolley to rest. The equipment on the trolley may be damaged if the mean resultant force on the trolley is greater than 12 kN12\ \mathrm{kN}12 kN.
| type of end stop | stopping time in s |
|---|---|
| rigid | 0.12 |
| deformable | 0.40 |
Calculate the shortest stopping time that keeps the mean resultant force on the trolley within this limit, and determine which end stop would protect the equipment.