As a planet draws away from the sun in its orbit, the force between the sun and the planet decreases and the planet's speed decreases.
Here's a brief explanation:
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The gravitational force between the sun and the planet is given by Newton's law of gravitation, which states that the force decreases with the square of the distance between the two bodies. As the planet moves away from the sun, this distance increases, leading to a decrease in gravitational force.
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According to Kepler's laws of planetary motion, particularly the conservation of angular momentum, the planet moves slower in its orbit when it is farther from the sun, especially if it is following an elliptical path. Thus, its speed decreases as it moves away from the sun.