Someone else mentioned the speed force business. When talking about the Flash, you have to divvy him up into three eras (at least):
Golden Age (Jay Garrick)
Silver/Bronze (Barry Allen)
‘80s and on (Barry Allen/Wally West/etc.)
I stopped reading during the Bronze Age, so I have only heard about the speed force business.
In the comics, all of them can run faster than the speed of light, so all physics goes out he door. However, there is a fun book called “The Physics of Superheroes” that looks at some of the Flash’s issues (how much would he have to eat for the energy he expends? LOTS. Can he run on water? Definititely, and at only 100MPH and up. Can he redirect or stop a bullet in mid air? Yes.).
The Silver/Bronze Age Flash was granted an invisible aura that keeps him from burning up. Besides that, he has control over every molecule in his body, and is able to vibrate his body to pass through most solid objects. He can also time travel by running faster than the speed of light (clockwise for the future, counter clockwise for the past, I don’t know if it is different in the southern hemisphere. He also made a treadmill to accommodate such travel.) Besides that, he has the ability to literally punch criminals into next week. I don’t know how he does that without killing them, or how he practiced that technique, but pretty cool, nonetheless.
Flash has an endless supplies of problems if you try to keep him in the realm of physics. Ultimately, almost all of these heroes turn from being 1938 Superman (very limited powers) into Fawcett’s Captain Marvel (it’s all magic).
The speed force also allows Flash to speed somebody’s speed. If a mugger is trying to run somebody down, Flash can touch them and have them move three times as fast and into a brick wall before they knew it.
I was denied comics as a child. Happened on Flash in Netflix and was hooked. Appreciate the comic eras history.