An airplane traveling at 510 km/h needs to reverse its course. The pilot decides to accomplish this by banking the wings at an angle of 38° while moving in a level circular path. Find the time needed to reverse course.
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8. Centripetal Forces & Gravitation
Banked Curves
Problem 49a
Textbook Question
A -kg car and a -kg pickup truck approach a curve on a highway that has a radius of m. At what angle should the highway engineer bank this curve so that vehicles traveling at mi/h can safely round it regardless of the condition of their tires? Should the heavy truck go slower than the lighter car?

1
Step 1: Convert the speed of the vehicles from miles per hour to meters per second. Use the conversion factor: 1 mi/h = 0.44704 m/s. Multiply 65.0 mi/h by 0.44704 to get the speed in m/s.
Step 2: Understand the concept of banking a curve. The angle of the banked curve is determined by ensuring that the centripetal force required for circular motion is provided entirely by the normal force and its components, without relying on friction. This is achieved using the formula: tan(θ) = v² / (r * g), where θ is the banking angle, v is the speed, r is the radius of the curve, and g is the acceleration due to gravity (approximately 9.8 m/s²).
Step 3: Substitute the values into the formula. Use v = the converted speed in m/s, r = 225 m, and g = 9.8 m/s². Calculate tan(θ) = v² / (r * g).
Step 4: Solve for θ by taking the arctangent of the result from Step 3. Use θ = arctan(v² / (r * g)) to find the angle in radians, and then convert it to degrees if necessary (1 radian = 57.2958 degrees).
Step 5: Address the second part of the question. Since the banking angle is designed to ensure safe travel at the given speed regardless of tire conditions, the mass of the vehicle does not affect the calculation. Therefore, the heavy truck does not need to go slower than the lighter car.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Centripetal Force
Centripetal force is the net force required to keep an object moving in a circular path, directed towards the center of the circle. For vehicles on a banked curve, this force is provided by the combination of gravitational force and the normal force acting on the vehicle. Understanding centripetal force is crucial for determining the necessary banking angle to ensure vehicles can navigate the curve safely without skidding.
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Intro to Centripetal Forces
Banking Angle
The banking angle of a curve is the angle at which the road is inclined relative to the horizontal. This angle helps counteract the gravitational force acting on the vehicle and provides the necessary centripetal force for circular motion. Calculating the optimal banking angle allows vehicles to maintain speed without relying solely on friction, which is particularly important in varying tire conditions.
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Banked Curve
Friction and Vehicle Dynamics
Friction is the force that resists the relative motion of solid surfaces, and it plays a critical role in vehicle dynamics, especially on curves. The amount of friction available between the tires and the road affects how fast a vehicle can safely navigate a curve. Heavier vehicles, like the pickup truck, may require more friction to maintain the same speed as lighter vehicles, influencing their safe speed on a banked curve.
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Releasing or Launching Projectiles From Moving Vehicles
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