physic
posted by pretty .
two of 5newton and 7newton respectively act on an object.when will the resultant of the two vectors be at a maximum?

Now this question in one form or another seems to be coming up here every few hours.
If you and your friends get together to push a sled, do you push in different directions?
Of course not, the magnitudes add with no nasty cosines of angles (cos 0 = 1, less than 1 for all other angles) between them when they are all in the same direction.
So you all push together and your forces simply add and that is the best you can do.
5+7 = 12