A ball is thrown vertically downward with a velocity of $30 \mathrm{~m} / \mathrm{s}$ from the top o

Question

A ball is thrown vertically downward with a velocity of $30 \mathrm{~m} / \mathrm{s}$ from the top of a tower. It hits the ground after some time with a velocity of $70 \mathrm{~m} / \mathrm{s}$. The height of the tower is $\left(g=10 \mathrm{~m} / \mathrm{s}^{2}\right)$

Professor PC Thomas Classes · Answer

(b): Here, $u=30 \mathrm{~m} / \mathrm{s}, v=70 \mathrm{~m} / \mathrm{s}, g=10 \mathrm{~m} / \mathrm{s}^{2}, h=$ ? \ $v^{2}=u^{2}+2 g h \Rightarrow 70^{2}=30^{2}+2 	imes 10 	imes h$. \ $4900 = 900 + 20h \Rightarrow 4000 = 20h$. Hence, $h=200 \mathrm{~m}$