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2.Motion in Straight Line
medium
A ball is thrown upwards. Its height varies with time as follows If the acceleration due to gravity is $7.5\, m/s^2$, then the height $h$ is.........$m$
A
$10$
B
$15$
C
$20$
D
$25$
(AIIMS-2011)
Solution
$\begin{array}{l}
Velocity\,at\,highest\,{\rm{point}}\,becomes\,zero\\
\therefore \,0 = u – at\\
or\,u = at\\
\,\,\,\,\,\,\,\, = \,7.5 \times 3.5 = 62.25m/s\\
\,\,\,\,\,\,\,\,\,{y_1} = u \times 1 – \frac{1}{2} \times 7.5 \times {1^2}\\
\,\,\,\,\,\,\,\,\,{y_2} = u \times 2 – \frac{1}{2} \times 7.5 \times {2^2}\\
\,\,\,\,\,\,\,\,\,h = {y_2} – {y_1} = 15
\end{array}$
Standard 11
Physics
