Which of the following is not true about centripetal force? check all that apply.
a. centripetal force keeps a car on the road going around a curve.
b. without centripetal force, an object would continue in a straight line.
c. centripetal force is the same as gravity.
d. it's also called an inward force.
e. it's the same as centrifugal force.

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.

You need to be more specific.  i really don't know what a "motion map" is.you can draw a graph of an object's position, distance, displacement, speed,velocity, or acceleration versus time, or you can draw a graph of the object's x-position versus its y-position and not give any information about time at all.if the graph presents position or displacement against time,  then constant velocity is a straight line . . i.e. a line that has  constant slope.if the graph shows speed against time, then constant velocityis a horizontal piece of line.if the graph shows acceleration against time, then constant  velocity is a piece of line that lies on the x-axis . . it's value is zero.