Skystar From Australia, joined Jan 2000, 1363 posts, RR: 3 Reply 1, posted (12 years 1 month 5 days 6 hours ago) and read 1898 times:
These are some rough whole numbers (just using some scenarios in my head).
A319 - 4 to 7kt/sec
B744 - 3 to 5kt/sec
Basically, if you want to work it out, just divide Vr by the takeoff time. Eg, rough figure for 744 at MTOW, 170/50=3.4kt/sec
A340 (269ton at ISA+12): 160/55=2.91kt/sec
There are so many factors which can affect this, because of weight and thrust derates involved. Some may be able to help you with the physics of it, but they tend to ignore other drag factors (generally consider only thrust & weight).