Answer
This is a writing exercise for the student, and answers will vary.
Sample:
Hey, Gramps! A net force applied on something at rest gets it moving in a straight line, and a net torque applied on something at rest gets it spinning. A force can produce a torque, for example, if it is applied at the rim of a turntable. The same force can produce different torques (for example, a force applied directly upon the axis produces no torque).
You know that swinging door in the kitchen? Push the surface, equally hard at the center and at the edge. You'll notice that it's much easier to turn the door when you push at the edge.
If you take a jar lid and twist it off, that's an example where the net force is zero (the forces on opposite sides cancel, and the lid's center doesn't move anywhere) but the torque isn't zero (because it starts turning).
Next, put your finger at the center of the lid and push it along the counter. Now you're exerting a net force, but no net torque.
