A torque of $50 \mathrm{Nm}$ acts on a body for 8 second which is initially at rest. The change in its…

A torque of $50 \mathrm{Nm}$ acts on a body for 8 second which is initially at rest. The change in its angular momentum is
  1. $400 \mathrm{kgm}^{2} / \mathrm{s}$
  2. $600 \mathrm{kgm}^{2} / \mathrm{s}$
  3. $1000 \mathrm{kgm}^{2} / \mathrm{s}$
  4. $800 \mathrm{kgm}^{2} / \mathrm{s}$

Solution

$\tau=50 \mathrm{Nm}$ for 8 second initially at rest $\vec{L}=\vec{\tau} \cdot t \quad$ for constant $\vec{L}$ $\vec{\tau}$ $|\vec{L}|=400 \mathrm{~kg} \mathrm{M}^{2} / \mathrm{S}.$

Asked in: MHT CET 2020 (15 Oct Shift 1)

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