# 17.33 Lord Kelvin and flying machines

William Thomson was one of the most famous physicists of the 19th century. He was born in 1824 and graduated in mathematics, from the University of Cambridge, in 1845. By 1846 he was Professor of Natural Philosophy (the contemporary name for physics) at the University of Glasgow in Scotland. He was made Sir William Thomson… Continue reading 17.33 Lord Kelvin and flying machines

# 17.32 How do birds fly?

Before you read this, I suggest you read posts 17.16 and 17.31. We often see birds flying without flapping their wings – they are gliding (post 17.31). In order to glide, their wing cross-sections must be shaped so that air moving over the wing has further to travel than air moving under the wing, so… Continue reading 17.32 How do birds fly?

# 17.31 Gliding and soaring

Before you read this, I suggest you read post 17.16. In post 17.16, we saw that a plane flies because, when it moves forward with a speed v, the pressure under the wing is greater than the pressure on top of the wing. The pressure difference, Δp creates an upward force, equal AΔp where A… Continue reading 17.31 Gliding and soaring

# 17.30 Collisions

Before you read this, I suggest that you read posts 16.13 and 16.21. If I drop a tennis ball on a hard, flat, smooth surface, it bounces back to almost the height it was dropped from. As it drops, it converts potential energy into kinetic energy; after it has bounced, it converts kinetic energy into… Continue reading 17.30 Collisions