Question

A stone is thrown upward from the edge of a cliff overlooking the ocean. The initial speed of the stone is 20m/s, and it's thrown up at an angel of 30 degrees with respect to the horizontal. the cliff is 45m above the ocean surface. How long is the stone in flight before striking the water?

Answer 1

in the vertical:
hf=hi+vi*t-4.9t^2
0=45+20*sin30*t-4.9t^2

put that in standard form for a quadratic
at^2+bt+c=0

use the quadratic equation

t=(-b+-sqrt(b^2-4ac))/2a