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271.

Which of the following fits can be used for selective assembly?

A.	Shrink fit	B.	Loose fit
C.	Free fit	D.	Medium fit

272.

Which is the variable stress

A.	Fluctuating	B.	Reversed
C.	Repeated	D.	Alternating
E.	All of the above

273.

The natural frequency of a shaft in bending is

A.	Nearly the same as the critical speed	B.	Nearly half the critical speed
C.	Nearly double of the critical speed	D.	Exactly the same at which it is running
E.	Depends on load and other factors

274.

At the first critical speed a shaft will

A.	Bend to the simplest shape possible	B.	Remain straight
C.	Bend to the convex form	D.	Bend to maximum permissible depth
E.	Vibrate producing audible sound

275.

A solid shaft and a hollow shaft are to be of equal strength in torsion. The hollow shaft is to be 10% larger in diameter than the solid shaft. The ratio of the weight of the hollow shaft will be (both shafts being made of same material)

A.	2	B.	1.2
C.	1	D.	0.6
E.	0.47

276.

A square key is

A.	More strong in shear and less strong in compression	B.	Less strong in shear and more strong in compression
C.	Equally strong in shear and compression	D.	Very weak in shear
E.	Very weak in compression

277.

If a square key and the shaft are to be of the same material and of equal strength, the length of key would be (d = dia. Of shaft)

A.	d	B.	0.75 d
C.	1.23 d	D.	1.50 d
E.	2 d

278.

In a standard coarse thread bolt the stress concentration is maximum at

A.	Root	B.	Top surface
C.	Flank	D.	Pitch circle
E.	All over the surface

279.

The coefficient of friction will be least in case of

A.	Metal on metal	B.	Wood on metal
C.	Leather on metal	D.	Asbestos on metal in oil
E.	Sintered metal on cast iron in oil

280.

A key and a shaft are made from the same material. The key is rectangular with a width of D/4 and a height of 3D/16. The shaft is under torsion only. The necessary length of the key for equal strength of the shaft and key will be

A.	D	B.	1.25 D
C.	1.57 D	D.	1.73 D
E.	2.00 D