Question

A stone is thrown vertically upwards. When stone is at a height half of its maximum height, its speed is $10m/s;$ then the maximum height attained by the stone is (g= $10m/s^2$)

• A. $25m$
• B. $10m$
• C. $15m$
• D. $20m$

Answer 1

Answer: (B)

$10m$

Let maximum height be H. At H, v=0.

Thus, $0-u^2=-2gH$

or, $u=\sqrt{2gH}$

Now, at H/2, v=10.

Thus, ${10}^2-u^2=-2g\left(H/2\right)$

or, $100-2gH=-gH$

giving, $H=\frac{100}{10}=10m$ (taking g=10)