Q1: 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

ANS:D - 90°

The instantaneous center 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 90°. In mechanisms or linkages, when the motion of a member is known, its instantaneous center is the point about which it appears to rotate at that instant. When two lines are drawn tangent to the path of motion of the two ends of a member, the point where these lines intersect is the instantaneous center. When the lines are perpendicular (90°) to the direction of motion at the ends of the member, the intersection point represents the instantaneous center. This occurs because the perpendicular lines are tangent to the circular paths that the ends of the member follow during motion.