ISRO Scientist or Engineer Mechanical 2013

Instructions

For the following questions answer them individually

Question 71

An oxidising process used for aluminium and magnesium articlesis called

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Question 72

Oneof the characteristics of Polymeris

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Question 73

Usually Materials with the following crystal structurefail in ductile mode

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Question 74

Work hardening strengthensan alloy by

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Question 75

An Aluminium object is made of a solid cone of height ‘h’ and base diameter D attached toa solid cylinder of diameter D and height ‘$$\frac{h}{2}$$’ as shown in figure. It is kept inclined touching to a vertical wall at point ‘A’ and hinged at. point B cr the floor. The object stays in this inclined position without going to vertical position (axis. perpendicular to the floor), only if. $$\theta$$ is less than

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Question 76

A hollow MSpipe is kept ona smoothstraight edge with the pipe mid pointsitting on it. A load “W’ Newtonsis applied at the ends which is keeping the pipe balanced in the horizontal condition. what is the safe maximum load ‘W’that can be applied withoutyielding the tube. Consider the self weight of the tube as ‘p’ $$\frac{N}{m}$$

Diameter of the pipe is 'd', Youngs modulus of pipe is E, Allowable yield stress is $$\sigma$$

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Question 77

A car crashes against a wall. Theinitial velocity at collision is 15$$\frac{m}{sec}$$ and the velocity after collision is 2.6$$\frac{m}{sec}$$ in the opposite direction. The massof the car is 1500kg. what is the average force exerted on the automobile bumperif collision lasts for 0.15 seconds.

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Question 78

Differential equation for the variation of amountof sait ‘x’ in a tank is given by :$$(\frac{dx}{dt} )+ (\frac{x}{20})$$ = 10. where x is in kg and t is in minutes. Assuming that at time zero thereis no salt in the tank, find the time at which the amountofsalt increases to 100kg

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Question 79

A5 mm diameter aluminium alloy test bar is subjected to a load of 560 N. if the diameterof the bar at this load is 4 mm,thetruestrain is

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Question 80

A material is dimensionally stable at room temperature if its glass transition temperature $$(T_{g})$$ is

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