# What is the net power of something

## Conservation of momentum and shocks

Note: The above formula can also be written in the form \ (F = \ frac {{\ Delta p}} {{\ Delta t}} \). It represents a generalization of the law of force \ (F = m \ cdot a \), since it describes not only the relationship between force and change in speed, but also the relationship between force and change in mass. This is of interest when the accelerated body does not maintain its mass (cf. rocket physics).

#### Applications

A certain change in momentum of, for example, \ (100 \, \ rm {Ns} \) can be achieved by applying a large force \ (1000 \, \ rm {N} \) for a short time of \ (0 {,} 1 \, \ rm {s} \) works. The momentum change can be achieved with a smaller force of only \ (100 \, \ rm {N} \). Here the force has to act for a longer time of \ (1 {,} 0 \, \ rm {s} \).

In the event of an accident, a driver's momentum can be reduced to zero by "slamming" his windshield. This process takes place in a very short time, the acting force is therefore correspondingly large.

If, on the other hand, the airbag is triggered, the driver's braking process takes place over a longer period of time, which means that the force acting is correspondingly smaller.

For this reason, climbing ropes have also been made elastic to a certain extent, so that if you fall into the rope, the braking process takes longer and the force on the person who has fallen is less.