A thin but rigid semicircular wire frame of radius r is hinged at O and can rotate in its own vertical plane. A smooth peg P starts from O and moves horizontally with constant speed v₀, lifting the frame upwards as shown in the figure. Find the angular velocity ω of the frame when its diameter makes an angle of 60^∘ with the vertical.
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For rigid rotation, relate angular speed using v=ω r.
Step 1: The peg constrains the end of the diameter to move horizontally with speed v₀.
Step 2: Linear speed of that point is related to angular speed:
v = ω r
Step 3: Hence
ω = (v₀)/(r)