Answer:
.12 N
Explanation:
Velocity goes from 2 m/s   to  0  m/s  so average velocity = 1 m/s
.250 m / 1 m/s  =  .25 second to stop
change in velocity / change in time = accel
 2 m/s / .25 sec =  8 m/s^2
F = ma
 = .015 kg *  8 m/s^2  = .12 N