Answer:
0.3 kg
Step-by-step explanation:
This can be dealt with using (a simplified version of) Newton's Second Law:
Force = mass x acceleration
We need to re-arrange the formula to get the mass of the ball isolated, on its own side of the equation. So we get:
mass = force/acceleration
So, now we just need to substitute the number we do have to get:
mass = 36/120 = 0.3 kg
Hope I helped! :)