An object is thrown from the ground with initial velocity 15 meters per second. It moves vertically according to $s = 15t – 4.9t_2$ where $s$ is in meters and $t$ in seconds, and $v$ is velocity and $a$ is acceleration, find:
a) $v$ and $a$ when $t = 4$ seconds. b) The maximum height. c) When its height will be 25 meters. d) When it hits the ground.
What would be the steps for solving that? I think these problems involve differentiating and substituting, but I'm not sure how to go about doing that.