GATE XE exam:gate PYQs & Answers — Page 147

Questions 1461–1470 of 1772. Imported answers require independent review unless marked reviewed.

On a flat plate, transition from laminar to turbulent boundary layer occurred at a critical Reynolds number (Re_cr). The empirical relations for the laminar and turbulent boundary layer thickness are given by

and

, respectively. The ratio of laminar to turbulent boundary layer thickness, at the location of transition, is 0.3. The value of Re_cr is ________.

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In a capillary tube of radius R = 0.25 mm, a fully developed laminar velocity profile is defined as,

. In this expression,

MPa/m, μ is the dynamic viscosity of the fluid, and r is the radial position from the center of the tube. If the flow rate through the tube is 100 mm³/s, the viscosity of the fluid, in Pa-s, is __________.

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The skin friction coefficient for a turbulent pipe flow is defined as,

, where τ_w is the wall shear stress and V is the average flow velocity. The value of C_f is empirically given by the relation:

, where Re is the Reynolds number. If the average flow velocity is 10 m/s, diameter of the pipe is 250 mm, kinematic viscosity of the fluid is 0.25×10⁻⁶ m²/s, and density of the fluid is 700 kg/m³, the skin friction drag induced by the flow over 1 m length of the pipe, in N, is __________.

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A (150 mm × 150 mm) square pillar is located in a river with water flowing at a velocity of 2 m/s, as shown in figure. The height of the pillar in water is 8 m. Take density of water as 1000 kg/m³ and kinematic viscosity as 1×10⁻⁶ m²/s. The coefficient of drag of the pillar is 2.0. The drag force exerted by water on the pillar in N is ________.

Diagram for Engineering Sciences question 21

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An orifice plate is used to measure flow rate of air (density = 1.23 kg/m³) in a duct of 250 mm diameter as shown in figure. The volume flow rate is 1 m³/s. Flow at sections 1 and 3 are uniform and section 2 is located at vena contracta. The diameter ratio, D_t/D_1, is 0.66. The flow area at vena contracta, A_2 = 0.65A_t, where A_t is area of the orifice. The pressure difference between locations 2 and 3 in N/m² is __________.

Diagram for Engineering Sciences question 22

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The stress ratio for a completely reversed cyclic loading during a fatigue test is

Your answerChoose one option.

−1

−1/2

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Minimum symmetry that a cubic crystal must possess is

Your answerChoose one option.

four 3-fold rotation axes.

three 4-fold rotation axes.

three orthogonal mirror planes.

centre of symmetry.

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If a material is repelled in an external magnetic field then it is

Your answerChoose one option.

Ferromagnetic

Diamagnetic

Paramagnetic

Antiferromagnetic

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An electron makes a transition from the valence band to the conduction band in an indirect band gap semiconductor. Which one of the following is true?

Your answerChoose one option.

Energy of the electron decreases.

A photon is emitted in the process.

A phonon is annihilated in the process.

A photon is created in the process.

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Which one of the following is the characteristic of a screw dislocation?

Your answerChoose one option.

Dislocation line and Burgers vector are parallel.

Direction of motion of dislocation is parallel to the Burgers vector.

Atomic displacement due to the movement of the dislocation is in the direction of the motion of the dislocation line.

It has a unique slip plane.

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GATE XE exam:gate PYQs

Question 18

Question 19

Question 20

Question 21

Question 22

Question 1

Question 2

Question 3

Question 4

Question 5