Question 65312
The equation that relates the height (as a funtion of time) of an object propelled upwards at an initial velocity of Vo from an initial height of Ho is:
{{{h(t) = -16t^2+Vot+Ho}}} Note the {{{t^2}}} in the first term.  Substituting t = 7, you get:
{{{h(7) = -16(7)^2+320(7)+0}}} Simplify.
{{{h(7) = -784+2240}}}
{{{h(7) = 1456}}}
The cannon ball will reach a height of 1,456 feet in 7 seconds.