Answer:
A
Step-by-step explanation:
Perpendicular lines have a relationship between their slopes. Their slope are negative inverses of each other. This means is one is 3 then the negative reciprocal is the other or -1/3. The slope here is 1/9 so the perpendicular slope is -9. Slope is always attached to the x term so A is the solution.
Yes it can be a direct variation. it follows the form y = kx
The only variable that cannot be held constant is F, but we can hold the mass constant and vary the acceleration OR we can hold the acceleration constant and vary the mass. Either one would work, but the easiest would be to vary the mass and hold the acceleration constant since we are all pulled by the same action gravity