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PART - 1 CH - 2 Motion in a Straight Line — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsPART - 1 CH - 2 Motion in a Straight Line2 Marks
Question
In the given figure the time-acceleration graph of an object moving in a straight line is given. Determined from graph :(i) Average acceleration in the first 20 sec.(ii) From what time tell what time the force acts on the object?Image
✓

Answer

 (i) Velocity change can be determined from time acceleration graph. This time is equal to the area between the acceleration graph and the zero acceleration axis. So in the first 20 sec .
$\begin{array}{l}
\text { Change in velocity }=\text { Area } ABCE \\
\text { Change in velocity }=\text { Area } A B F+\text { Area BCEF } \\
=\frac{1}{2} \times 10 \times 20+20 \times(20-10) \\
=100+200=300 m / s
\end{array}
$
Average acceleration
$\begin{array}{l}
=\frac{\text { Change in velocity }}{\text { Time interval }} \\
=\frac{300}{20}=15 m / s^2
\end{array}$
(ii) Force $=$ Mass $\times$ acceleration
If acceleration remains constant, force will also remain constant. It is clear from the graph that the acceleration remain constant from 10 sec to 20 sec . Hence the force on the object is 10 cm to 20 cm .

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