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# Force

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### Force

1. 1. Force <br />
2. 2. FORCE<br />Force: is either a push or a pull that acts on an object. <br />Whenever you bend, twist, stretch or compress something you are using a pushing or pulling force.<br />Force is an effect which can,<br />Start motion,<br />Stop motion,<br />Change the speed or direction of motion,<br />Change the shape or size of a body. <br />
3. 3. Unit of Force<br />Force is represented by the symbol F and is measured in Newton (N).The pull of the Earth on a 100 g mass is about 1 N.<br />
4. 4. Measuring Force<br />The force is measured by a spring balance or dynamometer.<br />
5. 5. Action and Reaction<br />For every action force, there is always an equal but opposite reaction force. If an object applies a force on a second object, then the second object will exert an equal but opposite force on the first object.<br />
6. 6. TYPES OF FORCE<br />There are many different kinds of forces:<br />Gravitational force<br />Magnetic force<br />Electrostatic force<br />Tension <br />Frictional force<br />
7. 7. Gravitational Force and Weight<br />Gravitational Force: The force of attraction between two objects due to their masses<br />Gravitational force depends on;<br />The masses of the objects,<br />The distance between them.<br />
8. 8. Gravitational Force and Weight<br />Gravitational force is directly proportional to the product of the masses: The greater the masses the greater the gravitational force. <br />Gravitational force is inversely proportional to the distance between the masses: The larger the distance between the objects the smaller the gravitational force.<br />The pull of the earth on a 1 kg mass is about 10 N<br />
9. 9. Weight <br />Weight (w): The gravitational force acting on an object. Since it is a force it is measured by a spring scale and its unit is Newton (N).<br />
10. 10. How does weight change?<br />The weight of an object on the earth depends on its distance from the earth's centre.<br />Near the earth, an object of mass 1 kg has a weight of about 10 N, whereas 22 000 km away from the centre of the earth, the weight of the object reduces to 1 N.<br />The weight of an object of 1kg weighs most at the poles (9.83 N) and least at the equator (9.78 N). A body having a weight of 600 N at the equator would have a weight of 603 N at the poles<br />
11. 11. How does weight change?<br />
12. 12. How does weight change?<br />The weight of an object also changes from one planet to another since g is different for different planets. However the mass of the object is the same in all planets.<br />
13. 13.
14. 14. MAGNETIC FORCE<br />Magnetic Force is the attractive or repulsive force between the poles of two magnets. <br />Like poles repel each other (b)<br />Unlike poles attract each other (a)<br />
15. 15. ELECTROSTATIC FORCE<br />Electrostatic Force is the attractive or repulsive force among electrically charged objects or electric charges such as electrons and protons. <br />
16. 16. TENSION<br />Tension (T): It is the pulling force in a rope or a chain.<br />
17. 17. FRICTIONAL FORCE<br />Frictional force: It is an important force which only acts when two objects are touching and are applying force to one another.<br />It is a force that slows down moving objects and brings them to rest. <br />It always acts in a direction opposite to the direction of the force applied to the object. <br />Walking is possible only on a frictional surface.<br />Water also applies a frictional force to the objects moving in it.<br />Frictional force does not depend on the area of the rubbing surfaces. <br />
18. 18. The frictional force between the object and the table depends on two factors;<br /> a) The weight of the object.<br />b) The roughness of the surfaces rubbing together.<br />