120. When a body moves round a fixed axis, it has

A. a rotary motion

B. a circular motion

C. a translator

D. a rotary motion and translatory motion.

121. The point about which combined motion of rotation and translation of a rigid body takes place, is known as

A. Virtual centre

B. Instantaneous centre

C. Instantaneous axis

D. Point of rotation

122. The locus of the instantaneous centre of a moving rigid body, is

A. straight line

B. involute

C. centroid

D. spiral.

123. If three rigid rods are hinged together to form a triangle and are given rotary as well as translatory motion, the number of instantaneous centres of the triangle, will be

A.1

B.2

C.3

D.4

124. The instantaneous centre of a member lies at the point of intersection of two lines drawn at the ends of the member such that the lines are inclined to the direction of motion of the ends at

A. 30?

B. 45?

C. 60?

D. 90?.

125. A rod 5 m in length is moving in a vertical plane. When it is inclined at 60? to horizontal, its lower end is moving horizontally at -sr3- m/sec and upper end is moving in vertical direction. The velocity of its upper end, is

A. 0.5 m/sec

B. 1.0 m/sec

C. 1.5 m/sec

D. 2.5 m/sec

126. (1.) rad/sec is the angular velocity of a crank whose radius is r If it makes 0? with inner dead centre and obliquity of the connecting rod I is 0, the velocity v of the piston, is given by the equation

A. (02(/ cos 41 + r sin (1) tan 0)

B. w2(/ sin (1) + r cos (1) tan 0)

C. (.0(/ sin (1) + r cos (1) tan 0)

D. o.)(1 sin (1) - r cos 0 tan (0).

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