Physics - Kinematics Question with Solution | TestHub

The acceleration of a marble in a certain fluid is proportional to the speed of the marble squared and is given (in SI units) by $\mathrm{a}=-\frac{v^2}{3}$ for $\mathrm{v}>0$. If the marble enters this fluid with a speed of $1.50\mathrm{m}/\mathrm{s}$, how long will it take before the marble's speed is reduced to half of its initial value?