15 seconds would probably be good for a 10 year old, or maybe in the 14s.
9.58 by Usain Bolt
Maurice Greene with a time of 9.87.
9.70 - 9.80 seconds.
Usain Bolt with a time of 9.58s.
it was shelly an fraser she won with 10.78 sec.
I just turned 13, I'm a little bit faster than average and I got 6.35. But the 40m sprint is completely irrelevent to 100m cause I got 15.72 in the 100m and my friend (who got 6.39 in the 40m) got 14.96. So the 40m sprint is just about accelaration not speed.
Sprint the 100m but do it with resistance, for example a parachute or weighted vest. Also make sure that you get completely stretched out before you time it, including your arms.
9.69secs done at the 2008 Beijing Olympics
Shelly-Ann Fraser of Jamaica in a time of 10.78 seconds.
Yulia Nesterenko of Belarus in a time of 10.93 seconds.