Help me with physics pls
Encke’s comet revolves around the sun in a period of just over three years. The closest it approaches the sun is 4.95 × 10^7 km, at which time its orbital speed is 2.54 × 10^5 km/h. At what distance from the sun would Encke’s comet have a speed equal to 1.81 × 10^5 km/h?
In 1981, Sammy Miller reached a speed of 399 km/h on a rocket-powered ice sled. Suppose the sled, moving at its maximum speed, was hooked to a post with a radius of 0.20 m by a light cord with an unknown initial length. The rocket engine was then turned off, and the sled began to circle the post with negligible resistance as the cord wrapped around the post. If the speed of the sled after 20 turns was 456 km/h, what was the length of the unwound cord?
Earth is not a perfect sphere, in part because of its rotation about its axis. A point on the equator is in fact over 21 km farther from Earth’s center than is the North pole. Suppose you model Earth as a solid clay sphere with a mass of 25.0 kg and a radius of 15.0 cm. If you begin rotating the sphere with a constant angular speed of 4.70 × 10^–3 rad/s (about the same as Earth’s), and the sphere continues to rotate without the application of any external torques, what will the change in the sphere’s moment of inertia be when the final angular speed equals 4.74 × 10^–3 rad/s?