- #1

Gian_ni

Moment of inertia changes during rotation. Calculate the work that changes kinetic energy?

Angular moment (along the axis of rotation) L = I * w

A point mass M rotates along an axis attached to a mass-negligible rod, of length r.

If someone moves the mass M at distance r / 2, the angular moment must conserve ( so

L1 = I2 w2 -> w2 = 4w1) , but kinetic energy is changed: ΔK = 0.5M (w2 ^ 2 * (r / 2) - w1 ^ 2 * r) = 0.5M * w1 ^ 2 * 7r

Since the work performed by the internal force (?) has increased, ΔK = W is positive.

- But what force in this case did the work and during which displacement?

- Is there a way to calculate the Work W without the work-energy theorem? Calculations?

Thank you