Rankers Physics

Friction: Practice Problem & Solution

An insect crawls up a hemispherical surface very slowly (see the figure). The coefficient of friction between the insect and the surface is 1/3. If the line joining the centre of the hemispherical surface to the insect makes an angle a with the vertical, the maximum possible value of α is given by : Friction diagram: An insect crawls up a hemispherical surface very
cot α = 3
tan α = 3
sec α = 3
cosec α = 3

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Friction. Understanding the underlying formula is key to arriving at the correct answer below:

For Equilibrium,

⇒ μmg cos θ = mg sin θ 

⇒ μ = tan θ = 1/3 

⇒ cot θ = 3 

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1. If the coefficient of friction between the block of mass 5 kg and wall is 0.5, then minimum force F required to hold the block with the wall is (g = 10 m/s²)
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