**841. If two forces each equal to T in magnitude act at right angles, their effect may be neutralised by a third force acting along their bisector in opposite direction whose magnitude will be**

A. 2 T

B. 1/2 T

C. ‘1T**D. 3T**

**842. If a body is acted upon by a number of coplaner non-concurrent forces, it may**

A. rotate about itself without moving

B. move in any one direction**C. move in any one direction rotating about itself**

D. all the above.

**843. The necessary condition of equilibrium of a body, is :**

A. algebraic sum of horizontal components of all the forces must be zero

B. algebraic sum of vertical components of all the forces must be zero

C. algebraic sum of the moments of the forces about a point must be zero**D. all (a), (b) and (c).**

**844. A smooth cylinder lying on its convex surface remains**

A. in stable equilibrium**B. in unstable equilibrium**

C. in neutral equilibrium

D. out of equilibrium

**845. A heavy ladder resting on a floor and against a vertical wall may not be in equilibrium, if**

A. floor is smooth and the wall is rough

B. floor is rough and the wall is smooth**C. floor and wall both are smooth surfaces**

D. floor and wall both are rough surfaces,

**846. Varigon’s theorem of moments states**

A. arithmetical sum of the moments of two forces about any point, is equal to the moments of their resultant about that point

B. algebraic sum of the moments of two forces about any point, is equal to the moment of their resultant about that point

C. arithmetical sum of the moments of the forces about any point in their plane, is equal to the moment of their resultant about that point**D. algebraic sum of the moments of the forces about any point in their plane, is equal to the moment of their resulant about that point.**

**847. A uniform rod 9 m long weighing 40 kg is pivoted at a point 2 m from one end where a weight of 120 kg is suspended. The required force acting at the end in a direction perpendicular to rod to keep it equilibrium, at an inclination 60? with horizontal, is**

A. 40 kg

B. 60 kg**C. 10 kg**

D. 100 kg.

**848. The centre of gravity of a plane lamina will not be at its geometrical centre if it is a**

A. circle

B. equilateral triangle**C.(b) rectangle**

D. right angled triangle.

**849. The centre of gravity of a homogenous body is the point at which the whole**

A. volume of the body is assumed to be concentrated

B. area of the surface of the body is assumed to be concentrated**C. weight of the body is assumed to be concentrated**

D. all the above.

**850. The centre of gravity of a quadrant of a circle lies along its central radius at a distance of**

A. 0.2 R

B. 0.3 R

C. OA R**D. 0.6R.**

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