# Why do different planets have different speeds

## Understand physics 4, textbook

32 2  Workbook page 19 32.1 Hubble space telescope 1. Which law of planetary motion did Johannes Kepler discover? As with Kepler - the elliptical orbit (Fig. 32.2) Set up the experiment as shown in Fig. 32.2. A strong magnet is at the focal point of the elliptical path. Set the iron model planet in motion. Observe the different speeds during the orbit. With V1 you can see that when the piece of iron approaches the magnet, its speed increases and decreases again as the distance increases. The speed of the earth during its orbit around the sun is also greater in the zone closer to the sun than in the area a little further away. The mean orbital speed of the earth around the sun is 30 km / s. The earth's orbit is an ellipse. In the time before Johannes Kepler it was believed that the orbits of the planets were exact circles. Through years of observation of the planet Mars and the evaluation of the data by the Danish astronomer Tycho Brahe, Kepler was able to recognize the true shape of the planetary orbits. M 1. Kepler’s law: The orbits of the planets are ellipses. The sun is at a focal point of these elliptical orbits. 2. How did Newton explain the planetary orbits? The curved orbits of the planets can only be explained by a central force. It is said that Newton came up with the idea of ​​a general gravitational pull through the observation of a falling apple. M A mass attraction or gravitational force prevails between the sun and the planets. It is centripetal force that keeps the planets on their elliptical orbit. 3. What does the magnitude of the gravitational force depend on? M The gravitation increases with the mass of the attracting bodies and decreases with the square of the distance. V1 Planetary Movement - Gravitational Force - Space Travel Sun Uranus Saturn Neptune Jupiter Venus Planetoid Belt Mars Mercury Earth 32.3 Orbits of the planets: Worldview according to Copernicus 0.4N 0.6N 1.1N 2.5N 10.0N 5 r 4 r 3 r 2 r 1 r Gravitational force 150t 150t 4m ≈ 0.1N sun earth 32.4 Decrease in weight of a body with a mass of 1 kg with the distance from the earth's orbit max. Speed: 30.29 km / s 147 million km 152 million km orbital time approx. 365d 6h min - speed: 29.29 km / s 32.5 Different speeds and distances when the earth revolves around the sun 32.6 Size comparison between sun and planets 32.2 As with Kepler - the elliptical orbit Focal points Iron piece e.g. electromagnet Jupiter Saturn Uranus Neptune Mercury Venus SUN Earth Mars worksheets 9c4nd3 For testing purposes only - property of the publisher öbv