Answer:
I think you mean what was the force applied on the cannonball, right? Well, that would be 75 N(newtons).
Step-by-step explanation:
F = ma(force = mass x acceleration). Plus in the values it would be...
F = m(10.0 kg) x a(7.5 m/s^2), or 75 kg/s^2/75 N(newtons). Easy math.