Final answer:
To decrease the force experienced by an object for a given change in momentum, the duration of time over which the force is applied should be increased. This concept is reflected by the formula that the average force is the change in momentum divided by the time interval.
Step-by-step explanation:
For a given change in momentum, you can decrease the force experienced by an object by increasing the time the force is applied over. Change in momentum is defined as the difference between the final and initial values of momentum, which is the mass times the change in velocity. An external force is a force applied to an extended object that changes the momentum of the extended object as a whole.
The relationship between force, change in momentum, and time is such that the average force applied to an object is equal to the change in the object's momentum divided by the time interval over which this change occurs. This implies that by extending the amount of time during which the force is applied, the same change in momentum can be achieved with a smaller force. This concept is crucial in preventing injury in events such as car crashes, where the time over which the collision occurs is increased through the use of crumple zones, therefore reducing the force experienced by the occupants.
In summary, a physical phenomenon that changes the momentum of an object, like a force, can cause the same change in momentum by acting for a longer period, thus reducing the magnitude of the force required.