Jordan throws a ball up vertically into the air. The ball leaves her hand at a speed of 15 m/s. How long does it take until the ball stops rising?

Answer 1

The ball stops rising when its instantaneous speed is zero. Use the kinematic relation

v(t) = v0 + at

v0 = 15 m/s

a = -g = -9.8 m/s^2

v(t) = 15 - 9,8t

Set v(t) equal to zero and solve for t.

15 - 9.8t = 0

You can finish from here.