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2.Motion in Straight Line
hard
A body thrown vertically up with initial velocity $52 \,m / s$ from the ground passes twice a point at $h$ height above at an interval of $10 \,s$. The height $h$ is .........$m$ $\left(g=10 \,m / s ^2\right)$
A
$22$
B
$10.2$
C
$11.2$
D
$15$
Solution
(b)
Given, $t_2-t_1=10 s$
$t_2+t_1=\frac{2 u}{g}=\frac{2 \times 52}{10}=10.4$
$\Rightarrow 2 t_2=20.4$
$\Rightarrow t_2=10.2 \,s$
$t_1=0.2 \,s$
So, $t_1 t_2=\frac{2 h}{g}$
$0.2 \times 10.2=\frac{2 \times h}{10}$
$\Rightarrow 1 \times 10.2=h \Rightarrow 10.2 \,m =h$
Standard 11
Physics