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Laws of Motion — PHYSICS STD 9 — Question

ICSE BoardEnglish MediumSTD 9PHYSICSLaws of Motion3 Marks
Question
A man sits in a machine which generates acceleration five times more than acceleration due to gravity. If the mass of man is 80 kg , what is his weight? Take $g =10 ms^{-2}$.
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Answer

$\begin{array}{l}\text { Mass of the man }= m =80 kg \\ \text { Acceleration due to gravity }= g =10 ms^{-2} \\ \text { Acceleration generated by the machine } \\ = a =5 g=5 \times 10=50 ms^2 \\ \text { Case-I: } \\ \text { When machine accelerates downward } \\ \text { Effective weight of the man = } mg - ma = m ( g - a ) \\ =80(50-10)=3200 N \\ \text { Case-II: When the machine accelerates upward } \\ \text { Effective weight of man = } mg + ma = m ( g + a ) \\ =80(10+50) \\ =80 \times 60=4800 N\end{array}$

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