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NEET Physics
QUESTION #1037
Question 1
A uniform rod of mass 20 kg and length 5 m leans against a smooth wall at \(60°\). Friction force from the floor is (Take \(g=10\ \text{m/s}^2\)):
Correct Answer Explanation
Taking torques about the contact point on the floor. The angle with the wall is \(60°\), so angle with floor is \(30°\). Normal from wall (horizontal) \(\times L\sin30° = mg\times\frac{L}{2}\cos30°\). Wait — using torque about foot: \(N_w\cdot L\sin30° = mg\cdot\frac{L}{2}\cos30°\Rightarrow N_w = \frac{mg\cos30°}{2\sin30°} = \frac{20\times10\times\frac{\sqrt{3}}{2}}{2\times\frac{1}{2}}=100\sqrt{3}\). Friction \(= N_w = 100\sqrt{3}\approx173\ \text{N}\). Answer: \(100\sqrt{3}\ \text{N}\).
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