The two important conservation laws are conservation of energy and conservation of momentum. From the concept of linear momentum and forces, impacts can be considered. ‘Newton’s Cradle’ and the “Galilean Cannon” are each illustrated with a simple JavaScript simulation. But we must also deal with angular momentum and couples. Although a displacement can sometimes be combined with a rotation, to give a rotation about a different axis, the result can often be a ‘screw’. In the same way, a couple and a force can either be combined into a force with a different line of action, or more generally into a ‘wrench’. Linear and angular momentum act together in an impulse, where the task can be to find the ‘sweet spot’ of a cricket bat.