Before you read this, I suggest you read post 21.3. A corkscrew is used to remove corks from a bottle – see the picture above. It is made by bending a metal rod, with a circular cross-section into a shape called a helix. The centroids of all the circular cross-sections lie on a helical line… Continue reading 21.6 The helix

Before you read this, I suggest you read post 21.3. In post 21.3 we met the simple spiral whose equation in polar coordinates is r = aθ                    (1) where a is a constant, r is the radius of the spiral and θ is an angle that is positive for anticlockwise rotation. In this post we… Continue reading 21.5 Logarithmic spirals