Engineering
Physics
Angular Momentum and Conservation of Angular Momentum
Question

A thin uniform rod, pivoted at O, is rotating in the horizontal plane with constant angular speed ω, as shown in the figure. At time t = 0, a small insect starts from O and moves with constant speed v with respect to the rod towards the other end. If reaches the end of the rod at t = T and stops. The angular speed of the system remains ω throughout. The magnitude of the torque (|τ|)  on the system about O, as a function of time is best represented by which plot?

 

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Solution

 τ=dLdt=ddt(l+mx2)ω=m×2xdxdtω=2mωv2t   [as   x=vt]