Physics

Problem

A stone is thrown vertically upward with initial speed

30\,\text{m/s}

. Taking upward as positive and

g=9.8\,\text{m/s}^2

, its velocity after

4\,\text{s}

is closest to a)

+9.2\,\text{m/s}

+69.2\,\text{m/s}

-9.2\,\text{m/s}

-49.2\,\text{m/s}