# Angular momentum of rigid bodies,When to add (moment of inertia*angular velociy)

The rigid 30-lb plank is struck by the 15-lb hammer
head H. Just before the impact the hammer is gripped
loosely and has a vertical velocity of 75 ft>s. If the coefficient
of restitution between the hammer head and the plank is
e = 0.5, determine the maximum height attained by the 50-lb
block D. The block can slide freely along the two vertical
guide rods. The plank is initially in a horizontal position.

link to diagram :

I applied the conservation of angular mom. thm, but after checking the solution manual ,
I realized that they applied the thm but adding for the whole system ,they took for the plank ,hammer, and block, m(Vg)*(distance to point B) , BUT (this is my real quistion ) ,for the plank they did , [m(Vg)*(distance to point B)] +[Ig*w] ......my quistion is why was'nt the Igw term added for the block and hammer ,and why was it added to the plank

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