what are ^j and ^i mean in physics?

I'm guessing those were carets written above the letter i and j. They're often read as "i-hat" and "j-hat" because the caret makes a little "hat" above the letter.

The hat notation stands for a unit vector. i-hat is the unit vector in the x-direction. So Fx*i^ is a vector of magnitude Fx in the x-direction. In other words, it's the x component.

Similarly, j-hat is the unit vector in the y direction.