A tennis ball is launched into the air at 20m/s. How high into the air will it go before it begins falling back toward earth?

Question

HELP! I need the exact answer to thus question please. This is something I need for in science. This will help me out alot if someone could give me the answer

Answer 1

Use the equation

 

-4.9t² + 20t = 0

 

 

Find the vertex of this equation by factoring out t.

 

-t(4.9t - 20) = 0

 

 

t = 0          and          4.9t - 20 = 0

                                 4.9t = 20

                                      t = 4.082

 

Take the average of the t values to find the x-coordinate of the vertex.  Then evaluate the equation at the vertex's x- coordinate to find the maximum height.