Drag Force on Plate due to Boundary layer

Q. The average drag coefficient for a laminar boundary layer over a flat plate was obtained as 0.018. If all other factors remain unchanged, and length of the plate is increased by 4 times its original value, this average drag coefficient would change to

1. 0.0036
2. 0.0056
3. 0.008
4. 0.009

Q. A thin smooth plate 1 m wide and 2 m long is towed through water at a velocity of 2 m/s. Assuming that boundary remains laminar, then drag on both sides of the plate is (kinematic viscosity = ${10}^{-6}{m}^2/s$)

1. 5.3 N
2. 26.6 N
3. 53 N
4. 72.5 N

Q. Consider a laminar flow at zero incidence over a flat plate.The shear stress at the wall is denoted by ${\tau }_w$. The axial position $x_1$ and$x_2$ on the plate are measured from the leading edge in the direction of flow.If $x_2>x_1$, then

1. ${\tau }_w{|{}_{x_1}={\tau }_w|}_{x_2}=0$
2. ${\tau }_w{|{}_{x_1}={\tau }_w|}_{x_2}\ne 0$
3. ${\tau }_w{|{}_{x_1}>{\tau }_w|}_{x_2}$
4. ${\tau }_w{|{}_{x_1}<{\tau }_w|}_{x_2}$

Q. A fluid with kinematic viscosity $\nu$ flows in laminar stage along a flat plate with free-stream velocity V. at a distance x from the leading edge, the Reynolds number of the flow is given by $R=\frac{Vx}{\nu }$. The thickness of the boundary layer at x will be proportional to

1. $x{R}^{1/2}$
2. $x{R}^{-1/2}$
3. $R^{1/2}$
4. $R^{-1/2}$

Q. What are the values of coefficient a and c if velocity distribution in a laminar boundary layer on a flat plat is:

$f\left(n\right)=\frac{u}{U_0}=a+bn+c{n}^2+d{n}^{3}where,n=\frac{y}{\delta }$

1. $\frac{1}{2}and1$
2. 0 and 1
3. $-\frac{1}{2}and0$
4. 0 and 0

Q. A smooth flat plate is in a parallel flow stream. The ratio of the drag over the upstream half of the plate to that over the entire plate is ... Assume the average skin friction coefficient is proportional to $(R{e}_x{)}^{-1/2}$.

1. 0.707