Communications satellites are placed in a circular orbit where they stay directly over a fixed point on the equator as the earth rotates. These are called geosynchronous orbits. The radius of the earth is 6.37 x 106 m, and the altitude of a geosynchronous orbit is 3.58 x 107 m (≈ 22,000 miles). What are (a) the speed and (b) the magnitude of the acceleration of a satellite in a geosynchronous orbit?

Ch 04: Kinematics in Two Dimensions

Knight Calc - Physics for Scientists and Engineers 5th Edition

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Knight Calc 5th Edition

Ch 04: Kinematics in Two Dimensions

Problem 68

Chapter 4, Problem 68

Communications satellites are placed in a circular orbit where they stay directly over a fixed point on the equator as the earth rotates. These are called geosynchronous orbits. The radius of the earth is 6.37 x 10⁶ m, and the altitude of a geosynchronous orbit is 3.58 x 10⁷ m (≈ 22,000 miles). What are (a) the speed and (b) the magnitude of the acceleration of a satellite in a geosynchronous orbit?

Verified step by step guidance

Step 1: Calculate the total radius of the satellite's orbit. The total radius is the sum of the Earth's radius and the altitude of the geosynchronous orbit. Use the formula:

r = R_{e} + h

, where

R_{e}

is the Earth's radius and

h

is the altitude of the orbit.

Step 2: Determine the orbital period of the satellite. For a geosynchronous orbit, the orbital period is equal to the Earth's rotational period, which is 24 hours. Convert this time into seconds using the formula:

T = 24 \times 60 \times 60

Step 3: Calculate the orbital speed of the satellite. Use the formula for circular orbital speed:

v = \frac{2 π r}{T}

, where

r

is the total radius of the orbit and

T

is the orbital period.

Step 4: Calculate the centripetal acceleration of the satellite. Use the formula:

a = \frac{v^{2}}{r}

, where

v

is the orbital speed and

r

is the total radius of the orbit.

Step 5: Verify the results conceptually. Ensure that the calculated speed and acceleration are consistent with the requirements of a geosynchronous orbit, where the satellite remains stationary relative to a point on the Earth's surface.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Geosynchronous Orbit

A geosynchronous orbit is a circular orbit around the Earth where a satellite's orbital period matches the Earth's rotation period, approximately 24 hours. This allows the satellite to remain fixed over a specific point on the equator, making it ideal for communication purposes. The altitude of such an orbit is about 35,786 kilometers above the Earth's surface.

Centripetal Speed

Centripetal speed is the constant speed required for an object to maintain a circular path. It is determined by the radius of the orbit and the gravitational force acting on the satellite. The formula for centripetal speed (v) in a circular orbit is v = √(GM/r), where G is the gravitational constant, M is the mass of the Earth, and r is the distance from the center of the Earth to the satellite.

Centripetal Acceleration

Centripetal acceleration is the acceleration directed towards the center of a circular path, necessary for an object to maintain its circular motion. It can be calculated using the formula a = v²/r, where v is the orbital speed and r is the radius of the orbit. This acceleration is crucial for understanding the forces acting on satellites in orbit.

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