Physics
posted by Jessica .
A hot air balloon is rising at a constant velocity of 13.3 m/s. When the balloon is at a height of 15 m, a heavy object is dropped overboard. IF air resistance on the object is neglected, how long does it take for it to reach the ground?

s = 15 + 13.3t  4.9t²
solve for s=0 
i don't get how to get rid of all the t's...

0=15+13.3t4.9t^2
it is a quadratic equation, use the quadratic formula.