Mass (m) = 150 g or 0.150 kg
initial velocity (u) = 25 m s-1
Final velocity (v) = 0
Time (t) = 0.03 s
The 1st equation of motion states that;
v = u + at
⇒ 0 = 25 + a × 0.03
⇒ a × 0.03 = -25
⇒ a = -25/0.03 m s-2 = -833.33 m s-2
Now,
Force (f) = mass (m) × acceleration (a)
= 0.15 × -833.33 = -125 N
Hence,
Magnitude of force = -125 N