A rider moves in a horizontal circle of radius 8 m inside a Well of Death with speed 20 m/s. Take g = 10 m/s². If the minimum coefficient of friction required is μ_min = N/5, find N.
Physics · Circular Motion · friction and circular motion
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Question

A rider moves in a horizontal circle of radius 8 m inside a Well of Death with speed 20 m/s. Take g = 10 m/s². If the minimum coefficient of friction required is μ_min = N/5, find N.

G1 Physics · Accepted Answer

For vertical equilibrium, friction must be able to balance the weight: mg ≤ μN_R. Since N_R = mv²/r, the limiting condition is mg = μ_min mv²/r. Hence μ_min = rg/v² = 8×10/20² = 80/400 = 1/5. Therefore N = 1.