Is it linear or nonlinear?

Question

A football is placed on the ground to kick a field goal. The height of the ball is a function of the time in seconds. Does the path the football follows after being kicked represent a linear or nonlinear function?

Answer 1

You can solve this problem without using any numbers at all. Let's think about a function where the X axis is time and the Y axis is height of the football as the question asks. Right after the ball is kicked the function goes from (0,0) to a point with positive X and Y values as time has passed and the football has risen in height. If this were a linear function the football would keep rising in height forever right? So this is not a linear function.