My textbook says that concurrent forces have no turning effect, but I don't quite understand this.
What are the conditions under which this applies?
If I hold a pencil horizontally and then drop it, the only considerable force acting on it is the force of gravity. If, while it's falling, I then hit it at one end, obliquely downwards, it spins. And yet the direction in which I applied the force and the direction of gravity are concurrent.
What am I missing??? (probably something very simple, but I will be grateful for any help).