alleryStart learning →What is the rotational analogue of Newton's second law?
Anet torque equals I divided by alpha
Bnet torque equals I times alpha
Cnet torque equals alpha divided by I
Dnet torque equals I times omega
Answer & Solution
Correct answer: B. net torque equals I times alpha
1. In F = m a, force drives acceleration and mass resists it.
2. Rotation has torque in place of force, moment of inertia in place of mass and alpha in place of a.
3. So net tau = I alpha, or equivalently alpha = net tau / I.
4. The relation holds for any torque, on any object, about any axis.
5. Writing I times omega gives angular momentum instead, which is a different quantity.
_Source: OpenStax College Physics (CC BY 4.0), Ch 10 "Rotational Motion and Angular Momentum", section 10.3 Dynamics of Rotational Motion: Rotational Inertia_
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