Why do we use machines in physics

In the most general sense, a machine is any device that can be used to perform a task. In the mechanical sense, a machine is a device for transmitting work from one location to another. ... Our muscles do work on our bones which in turn do work on the world around us. A doorknob is a machine.

magnitude and direction

the answer is neither ball has a charge.

because if they were both positively charged, they will repel each other.

if they were positively and negatively charged, they will seek.