Three different concentrations of fertilizer were used on corn plants. the weight of corn plants was measured after 6 weeks. what is the independent variable in the statement above?
the final weight of corn plants
the fertilizer concentration
the initial weight of corn plants
the percent weight change of corn plants from initial to final
the different kinds of fertilizer used

It depends on the surface of the levels. the rougher the surface, the greater is the frictional force. for rougher surfaces, you would need to exert greater force to move the object. the concept is that, you must overcome the frictional force in order to bring the object into motion. this is the reason why we add lubricants to the joints so they could easily move. this answer was on