Math Problem Statement

Assume the earth is spherical. Relative to someone on the rotation axis, what is the linear speed of an object on the surface if the radius vector from the center of the earth to the object makes an angle of 43.0° with the axis of rotation. The radius of the earth is 6.37×103 km.

Solution

To determine the linear speed of an object on the Earth's surface due to its rotation, we can use the following information:

  1. The Earth rotates once every 24 hours.
  2. The Earth is approximately spherical, and the radius from its center to the surface is R=6.37×103km=6.37×106mR = 6.37 \times 10^3 \, \text{km} = 6.37 \times 10^6 \, \text{m}.
  3. The angle between the radius vector and the axis of rotation is θ=43.0\theta = 43.0^\circ.

Steps:

  1. Angular velocity of Earth: The angular velocity ω\omega of the Earth is the same for all points and can be calculated as: ω=2πT\omega = \frac{2\pi}{T} where TT is the time for one complete rotation (24 hours, converted to seconds): T=24×3600=86400secondsT = 24 \times 3600 = 86400 \, \text{seconds} So, ω=2π86400rad/s=7.2722×105rad/s\omega = \frac{2\pi}{86400} \, \text{rad/s} = 7.2722 \times 10^{-5} \, \text{rad/s}

  2. Radius of the circular path: The object on the surface of the Earth makes an angle θ=43\theta = 43^\circ with the rotation axis. The radius rr of the circular path traced by this object is the projection of the Earth's radius onto the plane perpendicular to the axis of rotation: r=Rsin(θ)r = R \sin(\theta) where R=6.37×106mR = 6.37 \times 10^6 \, \text{m} is the Earth's radius. Thus, r=6.37×106×sin(43)r = 6.37 \times 10^6 \times \sin(43^\circ)

  3. Linear speed: The linear speed vv is related to the radius rr and the angular velocity ω\omega by: v=rωv = r \omega Substituting the values of rr and ω\omega, we can compute the linear speed.

Let's calculate that.The linear speed of the object on the Earth's surface, relative to someone on the rotation axis, is approximately 315.93m/s315.93 \, \text{m/s}.

Would you like further details or have any questions about the calculation?

Here are some related questions:

  1. How would the linear speed change if the object were located at the equator?
  2. What would be the effect on linear speed if the Earth rotated faster?
  3. How does the linear speed vary with different angles θ\theta from the rotation axis?
  4. Can this method be used to calculate the speed of artificial satellites orbiting the Earth?
  5. What is the relationship between linear speed and centripetal force in this scenario?

Tip: The farther from the rotation axis you are, the higher the linear speed due to Earth's rotation.

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Math Problem Analysis

Mathematical Concepts

Angular Velocity
Trigonometry
Circular Motion

Formulas

Angular velocity formula: ω = 2π/T
Radius of circular path: r = Rsin(θ)
Linear speed: v = rω

Theorems

Trigonometric projection for circular motion
Relationship between angular velocity and linear speed

Suitable Grade Level

Undergraduate Physics or Advanced High School (Grades 11-12)