This is an example of a motion blur. The shutter speed is 1/8. You can see the movement of the players because there’s a contrast between them versus the ones that are still.
This is an example of a frozen motion because the movement of the swing is frozen and not blurred if the shutter speed was at 1/8. This was shot in a shutter speed of 1/250 with a iso 100.
In your example of blurred motion, the bench in the front is nice a sharp. I know you were using a tripod to get it so sharp at 1/8th of a second.
1/250 does seem fast enough to capture the motion of someone in a swing. the photo is a little under exposed. next time raise the ISO if you have to just a stop 10>200 or 2 100>400.