Question #75636

Dec 2, 2016

Time needs to be a positive quantity.

Explanation:

The kinematic equation connecting quantities of interest is
$v = u + a t$

Inserting given values we get
$30 = 0 + 3.5 t$

Solving for time $t$ we get
$t = \frac{30}{3.5} = 8.57 s$, rounded to two decimal places, as given