A short bit explaining how forces cause something to rotate. The reason for doing so will become clear in another thread.
In (a) a force acts through the centre of mass of the object, causing it to be accelerated in a linear direction.
In (b) two equal and opposite forces act at a separation from the centre of mass. They cancel out in the linear sense, so there is no net movement of the object. However, this force (called a torque or a couple) causes the object to start to rotate.
In (c) an unbalanced force will cause the object both to start to move in the direction indicated by the force, *and* to rotate.
(d) Shows why - we add two imaginary forces to the body that cancel out overall. One of the imaginary forces taken with the real one gives the effect described in (b), the other force induces a net displacement as in (a).
Obviously spin bowling is all about applying rotary forces, but not just to the ball.... see Body Pivot - How (when I've written it).
In (a) a force acts through the centre of mass of the object, causing it to be accelerated in a linear direction.
In (b) two equal and opposite forces act at a separation from the centre of mass. They cancel out in the linear sense, so there is no net movement of the object. However, this force (called a torque or a couple) causes the object to start to rotate.
In (c) an unbalanced force will cause the object both to start to move in the direction indicated by the force, *and* to rotate.
(d) Shows why - we add two imaginary forces to the body that cancel out overall. One of the imaginary forces taken with the real one gives the effect described in (b), the other force induces a net displacement as in (a).
Obviously spin bowling is all about applying rotary forces, but not just to the ball.... see Body Pivot - How (when I've written it).