Free Download or read online Physics 9th ninth Class notes English Medium.Topic in this Notes Motion, Top Formulas, Force and Laws of Motion, Work and Energy, Sound, Gravitation. Some words from this notes is Key Learning: According to the law of gravitation the force of attraction between any two objects is proportional to the product of their masses and inversely proportional to the square of the distance between them. The law applies to objects anywhere in the universe. Such a law is said to be universal. Universal gravitational constant,Gravitation is a weak force unless large masses are involved…. If the position of an object does not change with time, it is said to be at rest. If the position of an object changes as time passes, it is said to be in motion. The reference point is a fixed point with respect of which a body is at rest or in motion. Rest and Motion are relative terms.The sound is a wave motion, produced by a vibrating source. A medium is necessary for the propagation of sound waves. The sound is a longitudinal wave in which the particles of the medium move along the direction of motion of the wave. The part or region of a longitudinal wave in which the density of the particles of the medium is higher than the normal density is known as compression. The part or region of a longitudinal wave in which the density of the particles of the medium is lesser than the normal density is called a rarefaction.The point of maximum positive displacement on a transverse wave is known as a crest.
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