- A$n$
- B$2n$
- C$\frac {n}{2}$
- ✓$\frac {n}{3}$
$\left(w_{0} / 2\right)^{2}=w_{0}^{2}-2\alpha Q$
$\left(w_{0} / 2\right)^{2}=w_{0}^{2}-2 \alpha Q_{1}$
$0=\left(w_{0} / 2\right)^{2}-2 \alpha Q_{2}$
$Q_{2}=\frac{Q_{1}}{3}$
$\Rightarrow \frac {n}{3}$
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Figure: $Image$
$1.$ The speed of the block at point $B$ immediately after it strikes the second incline is
$(A)$ $\sqrt{60} \mathrm{~m} / \mathrm{s}$ $(B)$ $\sqrt{45} \mathrm{~m} / \mathrm{s}$
$(C)$ $\sqrt{30} \mathrm{~m} / \mathrm{s}$ $(D)$ $\sqrt{15} \mathrm{~m} / \mathrm{s}$
$2.$ The speed of the block at point $\mathrm{C}$, immediately before it leaves the second incline is
$(A)$ $\sqrt{120} \mathrm{~m} / \mathrm{s}$ $(B)$ $\sqrt{105} \mathrm{~m} / \mathrm{s}$
$(C)$ $\sqrt{90} \mathrm{~m} / \mathrm{s}$ $(D)$ $\sqrt{75} \mathrm{~m} / \mathrm{s}$
$3.$ If collision between the block and the incline is completely elastic, then the vertical (upward) component of the velocity of the block at point $B$, immediately after it strikes the second incline is
$(A)$ $\sqrt{30} \mathrm{~m} / \mathrm{s}$ $(B)$ $\sqrt{15} \mathrm{~m} / \mathrm{s}$
$(C)$ 0 $(D)$ $-\sqrt{15} \mathrm{~m} / \mathrm{s}$
Give the answer question $1,2$ and $3.$