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Class 9 Science - The Fundamental Unit of Life (Cell) CELL:- Cells are the basic structural, functional, and biological units of all living organisms. They vary in size, shape, and function. Studying cells helps in understanding the life processes, growth, reproduction, and physiology of living beings. HISTORY OF DISCOVERY OF CELL:- 1. 1665: Robert Hooke observed cell walls in cork tissue under a microscope and coined the term 'cell'. 2. Anton van Leeuwenhoek observed living cells in pond water and other sources. 3. 1838-1839: Schleiden and Schwann proposed that all plants and animals are made of cells. 4. 1855: Rudolf Virchow stated that all cells arise from pre-existing cells.  CELL THEORY:-  *All living organisms are composed of one or more cells. * The cell is the basic unit of life, structure, and function. * Cells arise only from pre-existing cells. * The activity of an organism depends on the total activity of independent cells.  TYPES OF CELL:- 1. Prokaryotic ...

 DISTANCE:- *It is the total pathlength traveled by the body. *It is a scalar quantity. *SI unit is metre. *Distance=Speed/Time. DISPLACEMENT:- *It is known as change in position of an object. *It is a vector quantity. *SI unit is metre. *Displacement=Velocity/Time. UNIFORM MOTION VS NON-UNIFORM MOTION:- SPEED:- *Speed of an object is defined as the distance travelled by it per unit time. *It is a scalar quantity. *SI unit is metre per second (m/s). *Speed=Distance/Time. VELOCITY:- *Velocity of an object is measured as the displacement of the object per unit time. *It is a vector quantity. *SI unit is metre per second (m/s). *Velocity=Displacement/Time ACCELERATION:- *It is defined as the rate of change of velocity with respect to time. *a=final velocity (v) - initial velocity (u)/time.  *It is a vector quantity. *SI unit is m/s^2. GRAPHS:- 1.DISTANCE TIME GRAPH: 2.VELOCITY TIME GRAPH:- . KINEMATIC EQUATIONS:- 1. v=u+at 2.v^2=u^2+2as 3.s=ut+1/2at^2