a ball is at rest on a platform and falls freely, hitting the ground in 1.1 seconds. What is the height of the platform?

x_f = x_o + v_o t + 1/2 at²               (I used x as a matter of convention.....but you can switch them to 'y' )

 

xf = final height= the ground =  0

xo = intitial position (what we are looking for)

vo = original velocity = 0

a = accelaration of gravity    choose either  -32.2 ft/s²   your answer will be in feet

                                                  or choose  -9.81 m/s²    your answer will be in meters

 

t = time = 1.1   (given)           Plug in the numbers and calculate.....