i think for the solution we use \"Work done by gravity = change in rotational ki

Question

i think for the solution we use "Work done by gravity = change in rotational kinetic energy about pivot", but isnt this the formula?

how come they havent considered the kinetic energy of the the center of mass in the solution?

im really confused about this question, could someone explain in detail and also why we have to use the energy equation instead of kinematic eqation?

A meterstick (L = 1 m) has a mass of m = 0.223 kg. Initially it hangs from two short strings: one at the 25 cm mark and one at the 75 cm mark. After the right string is cut, the meterstick swings down to where it is vertical for an instant before it swings back up in the other direction. What is the angular speed when the meterstick is vertical? Delta(1/2 Mv2CM) + Delta(1/2 I Cm omega2) = W gravity

Explanation / Answer

the stick does not have any linear velocity as the string it is attached produces a force which restricts its linear movement so linear velocity of center of mass is zero but its torque produces rotational effect which is used in the conservation of energy equation so it should be Work done by gravity = change in rotational kinetic energy about pivot, no need for kinetic energy of the the center of mass in the solution since linear velocity is 0

we use energy equation instead of kinematic equation is becuase it is simple and elegant and since the gravity is conservational.we can also solve using kinematic eqation but it takes lot of time , involves many equations force,torque etc and messier.

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