Question

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: The drag coefficient is essentially constant with a value of 1.1 in the range of Reynolds numbers of 103 to 105. 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:

Answer 1

Answer:

Explanation:

Given

Coefficient of drag $C_d=1.1$

Reynolds number $Re.no.=103 to 105$

velocity $v=2 m/s$

$F_d=3 N$

if velocity if 2v i.e. $4 m/s$

$F_d=\frac{1}{2}C_d\rho A v^2----1$

keeping other factors as constant

$F'_d=\frac{1}{2}C_d\rho A (2v)^2----2$

dividing  1 and 2

$\frac{F_d}{F'_d}=\frac{v^2}{2v^2}$

$F'_d=4F_d$

$F'_d=4\times 3=12 N$