Usually I let scientific errors in comics roll off my back like complaints off a Southwest Airlines Customer Service representative. I mean after all, when you're dealing with a book where people can fly and have x-ray vision, complaining about the speed of light being unbreakable is a little hypocritical.
But occasionally I come across one I feel the need to comment on. In JSA 36, Jesse Quick and Baroness Blitzkrieg are having a brief high-speed chase/fight. Baroness B remarks that she doen't have to engage in fisticuffs with Jesse, she only has to "spread a number of obstacles in your path". She pulls a bunch of super-bounce balls from her satchel and tosses them in Jesse's path. The result, as Baroness explains that at the speed she's running, they hit her like bullets. Good idea.
Small problem. At the time she releases them, they're both running, at almost the same exact speed. If two objects are traveling at the same speed, relative to each other, they aren't moving. If one is moving at 500 MPH and the other at 501 MPH, the second one is only moving at 1 MPH, relative to the first.
So if Baroness releases the balls (there's no way to write that without sounding dirty), they're traveling at the same speed as the two runners, and in the time it takes for Jesse to plow into them, they haven't slowed down enough to strike her with much velocity at all. They'd be minor annoyances. Still something that could make her lose her stride and tumble (especially considering she's relatively new to speedstering, and doesn't have the reflexes, friction aura or ability to vibrate through obstacles of the flashes), but not enough to hit her "with the force of wrecing balls". If Blitzkrieg had been standing still and done the same, then yes, Jesses would have plowed into them at whatever speed she was running, and would have hurt like hell. Indeed, they might have just cut right through her, were she not able to avoid them. Of course, being bouncy-balls, a few might have bunced right back at Blitzkrieg and hit HER at Jesse's speed, having absorbed her kinetic energy. So, not as good an idea. Still, an elegant move, as Baroness calls it, tho.
I recall a story decades back that dealt with relativistic speeds of moving objects that got it RIGHT, but nobody could understand why it worked. John Ostrander did a mini about the cops of Gotham City (might have been called GCPD; too lazy to look it up). In the last scene there was a riot which the cops quickly quelled. Gordon mentions there were guns in the crowd, but most shots were fired in the air and injuries were from bruises as the bullets fell back down from the sky. People on Compuserve (an antiquated communication system similar to smoke signals) were asking how those bullets didn't kill anyone. After all, they're bullets.
I had to step in and explain that John had gotten it right, as he usually does. If a bullet is fired straight up, gravity starts to slow it down at the rate of g, or 9.8 meters per second per second. Once it comes to a halt, it starts to fall back down at that speed, but the bullet does not now have the terrific force of the gun's propulsion behind it. It's going to come down as it it had just been dropped from that height, which considering its small size and air resistance, is going to cause no more than a sharp sting if it hits anyone.
As you can see, I clearly have too much time on my hands.