Centre of Mass 3 Question 22
25. The speed of the block at point $C$, immediately before it leaves the second incline is
(a) $\sqrt{120} m / s$
(b) $\sqrt{105} m / s$
(c) $\sqrt{90} m / s$
(d) $\sqrt{75} m / s$
$(2008,4 M)$
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Answer:
Correct Answer: 25. (b)
Solution:
- Height fallen by the block from $B$ to $C$
$$ h _2=3 \sqrt{3} \tan 30^{\circ}=3 m $$
Let $v _3$ be the speed of block, at point $C$, just before it leaves the second incline, then :
$$ \begin{aligned} v _3 & =\sqrt{v _2^{2}+2 g h _2} \\ & =\sqrt{45+2 \times 10 \times 3} \\ & =\sqrt{105} ms^{-1} \end{aligned} $$
