Problem 15. The acceleration of a marble in a fluid is proportional to its velocity squared and is given by a = -3v² for v > 0. If the marble

enters the fluid with a speed of 1.5 m/s, how long will it take for the marble's speed to be reduced to half its initial value? Hint: Don't forget that a = dv/dt Rearrange the equation so you can integrate one side over velocity and the other side over time.