Which Conservation Law Do I Use for a Hanging Rod Hit by a Particle?

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In rigid body dynamics, momentum conservation is applicable when there are no impulsive forces acting on the system, while angular momentum conservation is valid as long as there is no torque about the pivot point. For a rod hanging from a pivot that is struck by a particle inelastically, the appropriate conservation law to use would depend on the nature of the forces involved. If the impact creates an impulsive force, momentum conservation should be applied. Conversely, if the system experiences no torque, angular momentum conservation can be utilized. Understanding the conditions for each conservation law is crucial for solving such problems effectively.
zhenyazh
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hi
in rigid body questions are there cases where i should use moment conservation
and not angular moment conservation or the opposite?

when would i use which?
 
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Good question. Use momentum conservation only when there is no impulsive force on your assumed system, or a non-impulsive force for conservation over a long period of time.Angular momentum conservation holds as long as there is no torque about the point.

Here's then a question for you. A rod hanging from a pivot is hit with a particle(inelastically).What would you use?
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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