How to make this cannon ball script kill players or NPC's?

What I mean, is how would I make this do 150 damage when it hits a player or a NPC? Also how to make it have a 2/4 chance of breaking that enemies joints if their MaxHealth is less than 1000?

pellet = script.Parent


function onTouched(hit)
	humanoid = hit.Parent:findFirstChild("Humanoid")
	if humanoid~=nil then
		g = Instance.new("Explosion") 
		g.ExplosionType = Enum.ExplosionType.NoCraters
                g.Parent = game.Workspace 
                g.Position = script.Parent.Position 
                g.BlastRadius = 5
                g.BlastPressure = 1000
                pellet:remove()
	       else
                script.Parent.PelletScript2.Disabled = false
                script.Parent.PelletScript:remove()	
	end
end



connection = pellet.Touched:connect(onTouched)