(1) In static and dynamic equilibrium, the body does not possess any

(a) Linear or angular acceleration                            (b) has linear acceleration but no angular acceleration

(c) Linear or angular momentum                (d) linear or angular velocity

(2) A body in equilibrium

(a) Can move with constant velocity                      (b) can move with constant acceleration

(c) Is always at rest                                                       (d) can move with variable acceleration

(3) To an observer on the ground, the passengers and bus on a straight road at constant velocity are an example of

(a) Static equilibrium                                                     (b) dynamic equilibrium

(c) Translational equilibrium                                        (d) none of these

(4) A body is said to be in translational equilibrium if the net force on it is

(a) Negative                                                                    (b) positive

(c) 0                                                                                  (d) decreasing

(5) If the axis of rotation doesn’t pass through the body the rotatory motion is said to be

(a) Circular motion                                                        (b) orbital motion

(c) Spin motion                                                               (d) Oscillatory motion

Note: Circular motion is a special case when the body is moving in a circle, that is, the distance of the trajectory of motion is always same from the center. In the orbital motion, however, it is not necessary.

(6) The point of intersection of the lines of action of the weights of all points of the body is

(a) Center of the body                                                  (b) center of mass of the body

(c) Center of gravity of the body                                             (d) none of these

(7) When a body is disturbed from its original position it falls away; the body is said to be

(a) stable equilibrium                                                    (b) dynamic equilibrium

(c) Neutral equilibrium                                                  (d) unstable equilibrium

(8) When a body is displaced from its original position it stays where it is placed, the body is said to be in

(a) Neutral equilibrium                                               (b) dynamic equilibrium

(c) Unstable equilibrium                                               (d) stable equilibrium

(9) When a body is displaced from its original position it returns back to its original position then it is said to be in

(a) Unstable equilibrium                                (b) stable equilibrium

(c) Neutral equilibrium                                                  (d) none of these

(10) Every point on a rotatory body has same

(a) Angular velocity                                                     (b) linear velocity

(c) Linear acceleration                                                  (d) linear momentum

(11) The perpendicular distance between the point of application of force and the fixed point or axis of rotation is called

(a) Moment of inertia                                                   (b) moment arm

(c) Momentum                                                               (d) torque

(12) In an equilibrium problem, the point about which torques are calculated

(a) Must pass through one end of the object          (b) must pass through object’s center of mass

(c) Must intersect the lines of action of at least one force acting on the object.

(d) May be located any where

(13) An object in equilibrium must not have

(a) Any acceleration         (b) any unbalanced force               (c) any torque acting on it             (d) all of these

(14) A pendulum at rest is in

(a) Unstable equilibrium  (b) neutral equilibrium     (c) stable equilibrium     (d) dynamic equilibrium

(15) A smooth sphere that is at rest on a table is in

(a) Unstable equilibrium  (b) neutral equilibrium   (c) stable equilibrium       (d) dynamic equilibrium

(16) Racing cars need a high degree of stability when turning bends on the race track. Which of the following features of these racing cars contribute to this stability?

(a) They are painted in bright colors                                         (b) their wheels have a wide base

(c) The drivers have personal protection   ensured (d) they run in high speeds

(15) If 2nd condition of equilibrium is satisfied the body is said to be in

(a) Translational equilibrium                                       (b) rotational equilibrium

(c) Static equilibrium                                                     (d) dynamic equilibrium

(16) If counter clockwise is taken as positive, then anti-clockwise is

(a) Positive                        (b) negative                        (c) doubled                         (d) halved

(17) To satisfy 1st condition of equilibrium, if rightward forces are taken as positive, the leftward forces will be

(a) Doubled                        (b) halved                           (c) positive                         (d) negative

#### (18) The point of intersection of the lines of action of the weight of all the points of body is called?

(a) Center of the body                    (b) center of mass of the body     (c) center of gravity        (d) none

(19) The relation between moment arm and moment of force is

(a) Directly proportional                              (b) inversely proportional              (c) equal               (d) none

(20) A mass of 70 g is attached at one end of the rod, and a mass of 30 g is attached at the other. The length of the rod is 60 cm, then the fulcrum should be placed ———- cm away from70 g mass for the rod to be balanced.

(a) 24 cm                            (b) 36cm                             (c)18 cm                             (d) 42 cm

Solution

Distance of 70 g mass from the fulcrum = x

Distance of 30 g mass from the fulcrum = y

X + y = 60 cm or x = 60 – y

In terms of torques,

70 x = 30 y  or 7 x = 3 y or 7(60 – y) = 3y

or 420  = 10 y or y = 42 or x = 60 – 42= 18 cm