It is from a fundamental kinematic equation s=v0t+(at^2)/2, s=distance, v0=initial speed, t=time, a=acceleration.
If you want to get the same distance covered in different time periods you need to change the velocity and the acceleration. Of course, we get a diophantine equation then, but we need this one most characteristic solution based on the values from previous tick.
So we could for example get an initial velocity of 100m/s, acceleration of 50m/s^2 and time of 2s. It gives us a distance of 300m.
Now let’s speed up things two times. To do that we need to cover the same distance of 300m but in twice shorter time period, 1s.
If we get the velocity and multiply it by 2 and the acceleration by 2 we get a distance of 250m. This is not the same distance as we get before, so something is wrong.
The thing is that in the formula the acceleration is multiplied by the square of time, not by time to the power of one like velocity. This is the reason why the acceleration must be multiplied by square of the number of times the time was dilated in order to preserve the initial distance that needs to be covered in shorter time.
Now if we multiply velocity by 2 and acceleration by 4 we get the result of 300m which is exactly what we wanted to get.
A simple another numerical example with the same values, but with four times speed-up:
1x time: 300=1002+(502^2)/2
4x time: 300=v0.5+(a0.5^2)/2=(notice that the time in acceleration fraction has now became 8 times smaller the it was in 1x time)=0.5v+0.25a/2
The solution which we want for this diophantine equation is v=400m/s and a=800m/s^2. The acceleration at 1x was 50m/s^2 and at 4x it is 800m/s^2. It was increased by 16 times, which is 4^2, so the acceleration must be multiplied by the square of time dilation.
I always say that if there is something already in the engine then don’t try to create your version of it, but simply use what the engine provides. UE4 has a powerful PhysX engine which allows for very realistic physical interactions (including splitting a destructible mesh) between objects and implementing these interactions myself will firstly take a lot of time and secondly will be most likely far worse than UE4 engine.
This is really the base reason why I mix maths and PhysX here.