Quiz: Mechanical Engineering 4th May

Quiz: Mechanical Engineering
Exam: DFCCIL
Topic: Fluid Mechanics

Each question carries 2 mark
Negative marking: 1/3 mark
Time: 10 Minutes

Q1. Capillary action is due to the
(a) Surface tension
(b) Cohesion of the liquid
(c) adhesion of the liquid molecules and the molecules on the surface of a solid
(d) All options are correct

Q2. The angle of contact in case of a liquid depends upon;
A. The nature of the liquid and the solid
B. The material which exists above the free surface of the liquid.
(a) Only A
(b) Only B
(c) Both A and B
(d) Neither A nor B

Q3. Alcohol is used in manometer because
(a) it has low vapor pressure
(b) it is clearly visible
(c) it has low surface tension
(d) it can provide longer column due to low density

Q4. _____will exhibit viscoelastic behavior.
(a) Steel
(b) Diamond
(c) Organic polymers
(d) Neoprene

Q5. In an experiment, the following shear stress-time rate of shear strain values are obtained for a fluid:

Time rate of shear strain (1/S)0234
Shear stress (kPa)01.42.64

How can the fluid be classified?
(a) Newtonian fluid
(b) Bingham plastic
(c) Pseudo plastic
(d) Dilatant

Q6. Free surface of a liquid behaves like a sheet and tends to contract to smallest possible area due to the
(a) force of adhesion
(b) force of cohesion
(c) force of friction
(d) force of diffusion

Q7. The vapor pressure over the concave surface is
(a) less than the vapor pressure over the plane surface
(b) equal to the vapor pressure over the plane surface
(c) greater than the vapor pressure over the plane surface
(d) zero

Q8. Consider the following statements;
1. Piezometer is used to measure small variation of pressure above or below ambient pressure.
2. Thixotropic fluid exhibits decrease in viscosity with time.
Which of the above statements is/are correct?
(a) only 1
(b) only 2
(c) Both 1 and 2
(d) Neither 1 nor 2

Q9. A fluid is defined as one which;
(a) cannot withstand shear
(b) can withstand elongation
(c) Deforms continuously when subjected to shear stress
(d) is solid-like when there is no motion

Q10. The most important property of a lubricant is its:
(a) viscosity
(b) pour point
(c) flash point
(d) thermal stability

S1. Ans.(d)
Sol. All three factors. i.e. surface tension of liquid, cohesion force in liquid and adhesive force b/w modulus of liquid and solid surface are responsible for capillary rise.

S2. Ans.(c)
Sol. The angle of contact depends upon both the cohesion force and adhesion force both.

S3. Ans.(d)
Sol. It is provided long column so error in pressure measurement is very less.

S4. Ans.(c)
Sol.

S5. Ans.(d)
Sol. We know that
τ=μ dv/dy
μ_1=τ/(dv\/dy)

μ_1=1.4/2=0.7pa.sec
μ_2=2.6/3=0.866 pa.sec⁡
μ_3=4/4=1 pa sec
We can see that μ_app is increasing which means n>1 for power low of viscosity. This is the condition for dilatant fluid.

S6. Ans.(b)
Sol. Free surface of liquid behave like a shunt this phenomenon gives by surface tension. Surface tension is nothing just unbalanced cohesive forces.

S7. Ans.(a)
Sol. There are two condition
(i) If curvature is convex, r is positive P > P_sat
(ii) If curvature is concave, r is negative P<P_sat.

S8. Ans.(b)
Sol. Piezometer is not able to measure pressure below ambient.
Thixotropic fluid- its viscosity decreases with time

S9. Ans.(c)
Sol. A fluid is defined as one which deforms continuously when subjected to shear stress.

S10. Ans.(a)
Sol.

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