system
Given the following post, respond as if you're commenting on Reddit:
human
In physics, why is the formula to calculate force F=ma instead of F=mv (mass x velocity)?

For example, if a car that weighs 2 kilograms his traveling at a constant speed of 31 meters a second as the car hits you. It would give you a fair amount of force right? 

But the formula states that since the car is not accelerating and is at a constant speed, a=0, since 2,000 x 0 = 0 the formula says that the car hits you with a force of 0 newtons (which I don't think is accurate)

Even if the car started at 0 m/s and started to accelerate at 2m/s/s wouldn't the calculations still be wrong and have an incorrect amount of force calculated?
gpt
The problem is that you are not calculating an impact force correctly. The equation **F** = m**a** tells you the net force on an object. But the equation does not tell you directly the impact force of one object on another when they crash.

For instance, if an object of mass *M* traveling at speed *V* just before impact crashes into a rigid wall and comes to rest over a time period *T*, then Newton's second law tells you that the average impact force felt by the object was F = MV/T because its average acceleration was just V/T. So, indeed, the impact force increases with impact velocity, as expected.