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OBJECTIVE TYPE QUESTIONS:, L., , The friction experienced by a body when at rest known as:, (a) static friction (b) limiting friction, (c) dynamic friction (d) coefficient of friction, A force acting in opposite direction to the motion of a body is called force of friction. It jg, (a) True (b) False., The maximum frictional force which comes into play when a body just begins to slide Over, the surface of other body is known as, , (a) Limiting friction (b) Dynamic friction, , (c) Static friction (d) all of the above., , The angle of inclination of the plane at which the body begins to move down the plane, is, , called, , (a) the angle of friction (b) the angle of repose, , (c) the angle of projection (d) all the above, , The minimum force required to slide a body of weight W ona rough horizontal p|, , (b) W Cos@, , ane 1S, , (a) W Sing, , (c) W tang (d) None of the these, , The static friction:, (a) always acts in a direction Opposite to that in which the body tends to move., , (b) is independent of the area of contact between the two surfaces and depends upon the, rough angles of the surfaces., , (c) bears a constant ratio to the normal reaction between the two surfaces., , (d) all the above., The force of friction which exist when the body is in motion is called, , (a) the static friction (b) the limiting friction, , (c) the dynamic friction (d) none of the above
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10., , Dyn -f, ynamie friction is always, , (a) More than the static friction (b) more than the limiting friction, , “ all the above, , less than the limiting friction (d), , If théaneiexce, "the angle ot friction is zero, , (a) the force of friction will be zero,, , (b) the force of friction will be infinite., , (c) the force of friction will act normal to the plane., (d) None of the above., , A bo ill bepi 3 A eT ‘, \ body will begin to move down an inclined plane if the angle of inclination of the plane is, , a the angle of friction,, (a) greater than (b) less than, (c) equal to (d) none of the above., , Kinetic friction may be defined as, , (a) The friction force acting when the body is in motion., (b) the ratio of limiting friction and normal reaction., (c) the friction force acting on the body is just about to move., , (d) none of the above., , On a ladder resting on the ground and leaning against a smooth vertical wall, the force of, friction acts,, , (a) Upwards at its upper end. (b) zero at its upper end, (c) downwards at its upper end (d) none of the above., , A body of weight W is resting on a horizontal plane. A force P is applied parallel to the plane, to move the body. The value of P necessary to move the body against the resistance of, , friction is, (a) W/tano (b) W sing, , (c) W tang (d) W Cos 6., , The coefficient of friction between two surfaces is a constant of proportionality between the, applied tangential force & the normal reaction., , (a) At the instant of application of force, , (b) At any instant of application of force.
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\, , lo, , I8., , ww) At the instant of impending motion, , (d) At the mstantatter motion tikes plies, , Coetherent of Kinetic tretion between a moving body and the surface on which at Moves, , (a) ts dependent on the velocity of body, , (b) depends only on the nature of the surtaces, , (c) depends on the nature of surfaces & the relative velocity between the surfaces &, body, , (d) depends on the nature of the surfaces, weight of the body and its velocity, , Che coefficient of friction between two surfaces is 0.2. Then the angle of friction ts, (a) sin! (0.2) (b) cos | (0.2), (c) tan! (0.2) (d) cot! (5), , Identity the correct statement:, , (a) Angle of repose — angle of friction, , (b) limiting friction = static friction., , (c) coefficient of friction — tangent of angle friction., , (d) tangent of angle of repose ~ coefficient of kinetic friction, , The angle which an inclined surface makes with the horizontal when a body placed it is on, the point of moving down is:, , (a) angle of friction (b) angle of inclination, , (c) angle of repose (d) none of these, , The acceleration of a body moving down a rough inclined plane of angle@ is equal to:(a) g tang (b) g sing, , (c) g (sin@-}H sing ) (d) g (sinQ- bcos 0), , Coefficient of friction is the ratio of, , (a) force of friction to reaction between bodies., (b) force of limiting friction to normal reaction between two bodies, (c) force of limiting friction to reaction between bodies., , (d) force of friction to normal reaction between two bodies.
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PP PCElOTE 45), , The coefficient of friction depends upon:, , (a) area of contact, , (b) shape of surfaces, (c) nature of surfaces (d) none of these, , Angle of friction () & angle of repose ( G, ) has the relation:, , @) a=6 (b) a>o/2, (c) a=2 (d) None of these, 33, _ Friction forces are, (a) Conservative forces (b) Non-conservative forces, (c) Pseudo forces (d) Inertia forces, 24. Frictional forces are area of contact., (a) directly proportional to (b) Inversely proportional, (c) Not proportional to (d) independent of., ANSWERS:1 (a), 2 (a), 3 (a), 4 (b), 5 (a), 5 ., 7 (c), 8 (c), 9 (a), 10 (a), 11 (a), 7 ,, 15 (c), 16 (c), 17 ©), ¢),, 13 (b), 14 (a), e na ea,, 19 (b), 20 (b), 21 (c), ;
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Determine the magnitude and direction of the friction force on a black weighting 125 Ke as, shown in fig 7.45, if P= 250N, p, =0.25 & py = 0.20. The forces are apres wits block, , initially at rest.
