- A$\pi / 2$
- B$\pi / 3$
- ✓$\pi$
- D$\pi / 4$
But if the angle between $\overrightarrow A $ and $\overrightarrow B $ is $0^°$. Then $\overrightarrow A \times \overrightarrow B = \overrightarrow B \times \overrightarrow A = 0$.
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If $v_1\,\,sin\,\,\theta _1 = v_2\,\,sin\,\,\theta _2$, then choose the incorrect statement
${ }_6^{11} C \rightarrow{ }_5^{11} B +e^{+}+ v _e+0.96 \,MeV$
Assume that, positrons $\left(e^{+}\right)$produced in the decay combine with free electrons in the atmosphere and annihilate each other almost immediately. Also, assume that the neutrinos $\left(v_e\right)$ are massless and do not interact with the environment. At $t=0$, we have $1 \mu g$ of ${ }_6^{12} C$. If the half-life of the decay process is $t_0$, the net energy produced between time $t=0$ and $t=2 t_0$, will be nearly ........... $MeV$
