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JEE Main 2026 (28 Jan, Shift 2) · Angular Momentum & its Conservation

Angular Momentum & its Conservation question from JEE Main 2026 (28 Jan, Shift 2)

Q1JEE Main 2026 · 28 JAN · SHIFT 2Easy

Angular Momentum & its Conservation

When the position vector r⃗=xi^+yj^+zk^\vec{r} = x\hat{i} + y\hat{j} + z\hat{k} changes sign as −r⃗-\vec{r}, which one of the following vector will not flip under sign change?

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Answer: (d)

  1. Under r⃗→−r⃗\vec r \to -\vec r: v⃗=dr⃗/dt\vec v = d\vec r/dt, p⃗=mv⃗\vec p = m\vec v and a⃗\vec a all flip sign.
  2. L⃗=r⃗×p⃗→(−r⃗)×(−p⃗)=r⃗×p⃗\vec L = \vec r \times \vec p \to (-\vec r) \times (-\vec p) = \vec r \times \vec p, unchanged.
  3. So the answer is (d) angular momentum.
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