Fluid flows over a smooth cylinder. the diameter of the cylinder is d and the length normal to the flow direction is l. the drag coefficient is defined as:
cd⁢ = fdrag / 1/2⁢ rho⁢ u^2⁢ d⁢ l
the drag coefficient is essentially constant with a value of 1.1 in the range of reynolds numbers of 10^3 to 10^5. in this range, at a velocity of 2 m/s the drag force is 3 n. when the velocity is doubled to 4 m/s the drag force is