541. The necessary condition for forces to be in equilibrium is that these should be_____________________?
A. coplanar
B. meet at one point ;
C. both A. and B. above
D. all be equal
E. something else

542. If n = number of members and j = number of joints, then for a perfect frame, n =
A.J – 2
B.2j – 1
C.2j – 3
D.3j – 2

543. A single force and a couple acting in the same plane upon a rigid body_________________?
A. balance each other
B. cannot balance each other
C. produce moment of a couple
D. are equivalent
E. none of the above

544. A particle inside a hollow sphere of radius r, having coefficient of friction -rr can rest upto height of___________________?
A. r/2
B. r/A
C. r/%
D. 0.134 r
E. 3r/8

546. Coulomb friction is the friction between_____________________?
A. bodies having relative motion
B. two dry surfaces
C. two lubricated surfaces
D. solids and liquids
E. electrically charged particles

547. A projectile is fired at an angle 9 to the vertical. Its horizontal range will be maximum when 9 is__________________?
A. 0°
B. 30°
C. 45°
D. 60°
E. 90°.

548. Shear stress induced in a shaft subjected to tension will be__________________?
A. maximum at periphery and zero at center
B. maximum at center
C. uniform throughout
D. average value in center
E. none of the above

549. A key is subjected to side pressure as well at shearing forces. These pressures are called_________________?
A. bearing stresses
B. fatigue stresses
C. crushing stresses
D. resultant stresses
E. none of the above

550. The torsional rigidity of a shaft is expressed by the_______________?
A. maximum torque it can transmit
B. number of cycles it undergoes before failure
C. elastic limit up to which it resists torsion, shear and bending stresses
D. torque required to produce a twist of one radian per unit length of shaft
E. maximum power it can transmit at highest possible-speed

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