KCET · Physics · Laws of Motion
A body of mass \(0.05 \mathrm{~kg}\) is observed to fall with an acceleration of \(9.5 \mathrm{~ms}^{-2}\). The opposing force of air on the body is \(\left(g=9.8 \mathrm{~ms}^{-2}\right)\)
- A \(0.015 \mathrm{~N}\)
- B \(0.15 \mathrm{~N}\)
- C \(0.030 \mathrm{~N}\)
- D zero
Answer & Solution
Correct Answer
(A) \(0.015 \mathrm{~N}\)
Step-by-step Solution
Detailed explanation
From, Newton's laws of motion,
or
\(\begin{aligned}\mathrm{mg}-\mathrm{F}_{\mathrm{air}} &=\mathrm{ma} \\\mathrm{F}_{\mathrm{air}} &=\mathrm{m}(\mathrm{g}-\mathrm{a}) \\
&=0.05(9.8-9.5) \\&=0.015 \mathrm{~N}\end{aligned}\)
or
\(\begin{aligned}\mathrm{mg}-\mathrm{F}_{\mathrm{air}} &=\mathrm{ma} \\\mathrm{F}_{\mathrm{air}} &=\mathrm{m}(\mathrm{g}-\mathrm{a}) \\
&=0.05(9.8-9.5) \\&=0.015 \mathrm{~N}\end{aligned}\)
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