A planet follows an elliptical orbit that brings it as close as 21 million km to a star and as far as 75 million km from the star. At both of these locations the velocity of the planet makes a right angle to the direction to the star. If the planet's speed is 38 km/s when it is farthest from the star, how fast is it moving when it is closest to the star

Explanation:

In an elliptical orbit , the angular momentum of the planet remains constant because velocity of planet makes a right angle to the direction to the star .

mvr = constant .

mv₁r₁ = mv₂r₂

v₁r₁ = v₂r₂

v₁ x 21 = 38 x 75

v₁ = 135.71 km/s .

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