
An object moves with speed \( v_1 \), \( v_2 \), and \( v_3 \) along a line segment \( AB \), \( BC \), and \( CD \) respectively as shown in the figure. Where \( AB = BC \) and \( AD = 3 AB \), then the average speed of the object will be: 
A disc is rolling without slipping on a surface. The radius of the disc is \( R \). At \( t = 0 \), the topmost point on the disc is \( A \) as shown in the figure. When the disc completes half of its rotation, the displacement of point \( A \) from its initial position is: 