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Motion in One Dimension — PHYSICS STD 9 — Question

ICSE BoardEnglish MediumSTD 9PHYSICSMotion in One Dimension3 Marks
Question
A packet is dropped from a stationary helicopter, hovering at a height ' $h$ ' from ground level, reaches ground in 12s. Calculate
1. value of $h$
2. final velocity of packet on reaching ground. (Take $g =9.8 ms 2$ )
✓

Answer

$
\begin{array}{l}
\begin{array}{l}
\text { Height of the helicopter }=h=? \\
\text { Initial velocity }=u=0 \\
\text { Time }=t=12 s \\
\text { Acceleration }=a=+g=+9.8 ms^{-2} \\
S=u t+\frac{1}{2} a t^2 \\
h=0(12)+\frac{1}{2}(9.8)(12)^2 \\
h=0+4.9(144) \\
h=705.6 m
\end{array}\\
\text { Let } v=\text { velocity of the packet on reaching the ground. }\\
\begin{array}{l}
v=u+a t \\
v=0+(9.8) 12 \\
v=117.6 ms^{-1}
\end{array}
\end{array}
$

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