A rock is thrown upward with a velocity of 28 meters per second from the top of a 39 meter high cliff and it misses the clip on the way back down when will The

Question

College algebra 

Answer 1

The question is incomplete, but I assume you want to find when the rock strikes the ground.

 

h(t) = -4.9t² + 28t + 39  [t in sec, h in meters]

 

It strikes the ground when h(t) = 0.

 

Set h(t) = 0 and solve the resulting quadratic equation for t.  You will get a positive and a negative solution.  Since time starts at the moment of throwing the rock (t = 0), discard the negative solution.