1. The problem statement, all variables and given/known data In the setup , block C remains at rest and block A move towards left when system is released . If velocity of A is 'u' towards left at an instant , what is the vertical component of velocity with which B descends .What is the horizontal component of velocity of B at this instant ? Ans : Vertical component of velocity = (u/2)tanθ1 Horizontal component of velocity = (u/2) 2. Relevant equations 3. The attempt at a solution Block B is constrained to move along the contact surface with C . From the geometry it can be seen that when B moves vertically down by distance 'x' ,it is constrained to move by a distance xcotθ1 towards left . By similar argument , suppose C is not present ,and B is somehow constrained to move exclusively in only vertical direction .If B moves down by a distance 'x' , A moves towards left by a distance xcotθ2 . Combining the two effects we can say if B moves down by a distance 'x' , A moves towards left by a distance xcotθ1 +xcotθ2 . Similarly If vertical speed of B is 'v' then speed of A is u = vcotθ1 +vcotθ2 . Now in the question we are given 'u' and asked to find 'v' and 'vcotθ1' . I am not sure how do I get 'v' and 'vcotθ1' in terms of u . Is the book answer correct ? Any help is appreciated . Thanks .