The 1kg ball would exert the smallest force.
As force = mass x gravity, this means that the smaller the mass (kg), the lesser the force.
When the mass is lighter (1kg):
Force = mass x gravity
Force = 1 x 9.8
Force = 9.8N
Compared to when the mass is heavier (10kg)
Force = mass x gravity
Force = 10 x 9.8
Force = 98N
Where this proves that the lighter the mass, the smaller the force exerted.