Originally Posted by

**ThePerfectHacker** The standard function is a quadradic:

s(t)=(-1/2)gtē+vt+h

v is initial velocity which is 860 feet per second which is going to be positive since it is going up.

h is initial height which is 7 feet.

g is the decelleration from gravity. Which is 32 feet per second per second.

Thus,

s(t)=-16tē+860t+7

~~~

The obejct reaches 100 feet when s(t)=100 for some value t.

Thus,

-16tē+860t+7=100

Thus,

-16tē+860t-93=0

Important. When you solve this using quadradic formula you shall get two values for t. Select the first one because the problem say "..going up...".

~~~

That is equivalent to saying amount of time until it comes down.

Solve

s(t)=0 for some positive t value.

Thus,

-16tē+860t+7=0

Apply quadradic formula.