Question

A ball is thrown downward 8 m/s. What is its speed 4 seconds later?

Answer 1

Task. A ball is thrown downward $v=8$ m/s. What is its speed 4 seconds later?

Solution. Notice that there is a gravitation force acting on the ball, so it moves with constant acceleration $g=9.8\ m/s^{2}$. Therefore the speed of the ball after $t$ seconds is given by the formula:

$v(t)=v_{0}+gt,$

where $v_{0}=8\ m/s$ is the initial velocity.

We should compute $v(4\ s)$. Substituting values we get:

$v(4)=v_{0}+gt=8+9.8*4=47.2\ m/s.$

Answer. $v=47.2\ m/s.$