This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Horizontal and Inclined Plane Surface Submerged in a Liquid”.

1. Find the total pressure on a rectangular plate of dimensions 2×3 m immersed in a fluid of specific gravity 0.65 at a depth of 6 m from the surface.

a) 22.9 N/cm^{2}

b) 45.8 N/cm^{2}

c) 11.5 N/cm^{2}

d) None of the mentioned

View Answer

Explanation: Total pressure, F=w*a*y

=9.81*650*6*2*3

=22.9 N/cm

^{2}.

2. Find the total pressure on a circular plate of diameter 3 m immersed in a fluid of specific gravity 0.75 at a depth of 5 m from the surface on a planet having acceleration dueto gravity 7 m/s^{2}.

a) 18.5 N/cm^{2}

b) 37 N/cm^{2}

c) 9.25 N/cm^{2}

d) None of the mentioned

View Answer

Explanation: Total pressure, F=w*a*y

=7*750*π*1.5*1.5*5

=18.5 N/cm

^{2}.

3. A rectangular plate surface 3m wide and 5m deep lies in fluid of specific gravity .9 such that its plane makes an angle of 45⁰ with water surface, upper edge 3m below free water surface. Determine the total pressure.

a) 86.5 N/cm^{2}

b) 173 N/cm^{2}

c) 43.25 N/cm^{2}

d) None of the mentioned

View Answer

Explanation: Total pressure, F=w*a*ŷ=w*A*(y+dsinθ)=9.81*900*15*(3+5sin45)

=86.5 N/cm

^{2}.

4. A rectangular plan surface 5 m wide and 7 m deep lies in water in such a way that its plane makes an angle 60⁰ with the free surface of water. Determine the total pressure force when the upper edge is 3 m below the free surface.

a) 311.15 N/cm^{2}

b) 622.3 N/cm^{2}

c) 155.5 N/cm^{2}

d) None of the mentioned

View Answer

Explanation: Total pressure, F=w*a*ŷ=w*A*(y+dsinθ)=9.81*1000*35*(3+7sin60)=311.15 N/cm

^{2}.

5. A circular plate 5.0 m diameter is immersed in such a way that its greatest and least depth below the free surface are 3 m and 1 m respectively. determine the position of the centre of pressure.

a) 2.5 m

b) 5 m

c) 4.5 m

d) 6 m

View Answer

Explanation: centre of pressure, ŷ=I*sin²θ/Aĥ + ĥ

…….ĥ=(y+dsinθ)

=3.142*2.5

^{4}*sin²23.58/3.142*2.5

^{2}*(1+2.5sin23.58)+*(1+2.5sin23.58)

=2.5 m.

6. For an inclined plate the pressure intensity at every point differs.

a) True

b) False

View Answer

Explanation: Due to inclination the depth of every point is different from the free liquid surface. Hence, the pressure intensity varies with depth.

7. The pressure intensity for a horizontal plate is maximum on the surface of the earth and decreases as we move further away from the surface of the earth either downward or upward.

a) True

b) False

View Answer

Explanation: As we move away from the surface of the earth either downward or upward g decreases, w decreases. Hence pressure intensity decreases.

8. For an inclined plane for which position, maximum total pressure acts on it.

a) Horizontal

b) Vertical

c) Inclined

d) None of the mentioned

View Answer

Explanation: Total pressure, F=w*a*ŷ=w*A*(y+dsinθ)

For vertical plate, θ=90⁰

Hence, total pressure is maximum.

9. The total pressure or pressure intensity is zero for any point on inclined surface in space.

a) True

b) False

View Answer

Explanation: Total pressure, F=w*a*ŷ

In space, w=0 as g=0

Hence, f=0.

10. In case of spherical bodies with uniform mass distribution, what is the position of center of pressure relative to centre of gravity.

a) Above

b) Below

c) Coincides

d) None of the mentioned

View Answer

Explanation: In case of spherical bodies with uniform mass distribution, centre of pressure coincides with centre of gravity.

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