 channel for physics. Please subscribe my channel. Hello and welcome back to another episode of Physics Partner. Today's video is especially designed to cover new topics injected in the curriculum of physics for the Codes 0625 and 0972 by Cambridge IGCSE. The Earth is a rocky planet that rotates in a near circular orbital around the Sun. Let's understand the two terms rotation and revolution. Rotation refers to an object spinning motion about its own axis whereas revolution refers the object's orbital motion around another object. For example, Earth rotates on its own axis producing the 24 hour day. Earth revolves around the Sun producing the 365 day year. Let's talk about Earth mean orbital speed. Earth's mean orbital speed is the average speed at which the Earth revolves around the Sun. A rough general figure of the Earth mean orbital speed is about 30 kilometers per second. The average orbital speed of the object is actually defined by the equation. You can see the equation here which is v is equal to 2 pi r over t whereas v is orbital speed in meter per second. r is average radius of the orbits in meter. t is the orbital periods in second. Same way time period is also defined as the time taken of an object to complete one orbit. The orbital radius r is always taken from the center of the object being orbited to the object orbiting. The Moon does not produce its own light. We can only see the Moon because it reflects sunlight. The amount of the reflected sunlight that reaches the Earth is determined by the relative positions of the Earth, Moon and Sun and determine the phases of the Moon. Most of the time we have a partial view of Moon because the Sun does not light the whole of the side of the Moon as viewed from Earth unless the Sun, Moon and Earth are lined up in that order. This only happens once every 27 days the time the Moon takes to orbit the Earth once. The different appearances of Moon as seen from Earth are given different names. You can see here on the screen. So that's all for today. I hope you enjoyed the video. I hope this video is very useful for you. If you have any further question you can write an email. Thank you very much and see you in the next video. Goodbye.