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What is the safety speed for a vehicle moving along a curved horizontal banked road?

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The safety speed on a banked curve depends only on the radius of the curve, the acceleration due to gravity, and the banking angle. Friction is not considered in this case.
Updated On: Nov 26, 2025
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Solution and Explanation

Phase 1: Identification of Forces. The forces acting on a vehicle traversing a banked curve include:
  • Gravitational force (\( mg \)).
  • Normal reaction force (\( N \)).
  • Frictional force (\( f \)).
The resultant force dictates the centripetal force required for circular motion. Phase 2: Force Decomposition. The centripetal force is supplied by the component of the normal reaction force directed towards the center of the curve: \[ N \sin \theta = \frac{m v^2}{r}, \] wherein \( v \) represents velocity, \( r \) denotes the curve radius, and \( \theta \) signifies the banking angle. Phase 3: Idealized Scenario (Maximum Safe Velocity). In a frictionless scenario, the component of the normal force satisfies the centripetal force requirement: \[ v^2 = r g \tan \theta. \] The expression for \( v \) is: \[ v = \sqrt{r g \tan \theta}. \] Phase 4: Conclusion. The maximum safe velocity is: \[ \boxed{V = \sqrt{r g \tan \theta}}. \]
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