If Afghanistan's growth rate remains the same (which is very unlikely and the country's projected growth rate for 2025 is a mere 2.3%), then the population of 30 million would become 60 million in 2020, 120 million in 2035, 280 million in 2049, 560 million in 2064, and 1.12 billion in 2078!
The Mysticism of Downforce. Downforce is the secret voodoo of motorsports. If you don't embrace it, you won't be fast. We take a lesson in the Wolf GB08SM Turbo.
The force that is pulling the particle down is gravity, f = m*a. As the particle gets larger and denser, m (mass) increases. The opposing force is the friction of the water, which also increases with the size of the particle and its shape (with more friction as its surface area increases) . So for example, with two particles of the same mass and density, the one with the larger surface area (thus more friction) will settle slower. Two particles of the same size and shape, but different density, the one with the higher density (more mass) will settle faster.