The system consists of a 20-lb disk a, 4-lb slender rod bc, and a 1-lb smooth collar c. if the disk rolls without slipping, determine the velocity of the collar at the instant the rod becomes horizontal. the system is released from rest when ! = 45°.

The velocity of the collar will be 3.076 ft/s

Explanation:

Given data

weight of the disk, Wa = 20lb

weight of rod BC, Wbc = 4lb

weight of collar, Wc = 1lb

Considering the equation of equilibrium

Vb = 1.5Wbc

Wa = 1.875 Wbc

to calculate the velocity of the collar using energy conservation equation

T1 + V1 = T2 + V2

=>

=>

=>

Wbc = 1.18rad/sec

i.e.                                    

= 3.076 ft/ s

i think the answer is b

snell's law

refractve index = sin incidence / sin refraction