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2.Motion in Straight Line
easy
A stone thrown upward with a speed $u$ from the top of a tower reaches the ground with a velocity $4 u$. The height of the tower is .........
A
$\frac{15 u^2}{2 g}$
B
$\frac{7 u^2}{2 g}$
C
$\frac{16 u^2}{g}$
D
Zero
Solution
(a)
$v=\sqrt{u^2+2 g h}$
$(4 u)^2=u^2+2 g h$
$\frac{16 u^2-u^2}{2 g}=h \Rightarrow h=\frac{15 u^2}{2 g}$
Standard 11
Physics