Friction The force that opposes the relative motion between two surfaces in contact, is called friction. Factors affecting friction Weight of object Nature of surfaces in contact More the weight of object, more the friction. More smooth surface experience less friction. Importance of friction Friction helps in stopping object Friction helps to write, walk, Friction helps in all activities Friction produces heat. Harm cause by Friction Sole of shoes wear out. Machine parts get wear out. Friction can be increased by making surfaces rough. ( More rough means more interlocking between surfaces which means more friction ) Friction can be decreased by applying lubricant on surfaces. Friction can be decresed by changing shape of object. Rolling friction The force that oppose motion of rolling object, is rolling friction. Sliding friction The force that oppose moti...
Materials: Metals and Non-metals * Lustre - Lustre is physical property of substance by which it looks shiny. * Malleability - Malleability is property of metal, by which they can be beaten into thin sheets. * Ductility - Property of metal, by which they can be drawn into wires, is called ductility. * Good conductor of heat/electricity -The materials through which heat/electricity can pass, is called good conductor of heat/electricity. -Example- Iron. * Poor conductor of heat/electricity -The materials through which heat/electricity cannot pass, is called poor conductor of heat/electricity. - Example- Plastic * Sonorous - Metals are sonorous since they produce ringing sound. * Physical properties of metals and Non- metals ...
Acids The chemicals causing sourness of substance, is called acids . These are not soapy to touch. These turn blue litmus into red. Example- Acetic acid(chemical in vinegar) Bases The chemicals causing bitterness of substance, is called bases . These are soapy to touch. These turn red litmus into blue. Example- baking soda, calcium hydroxide etc. Indicator The substance used to test whether a substance is acidic or basic, are called indicator. Example- Turmeric, litmus, china rose petals, phenolphthalein etc. Litmus:A natural dye It is a natural indicator. It is extracted from lichen. When added to acid, it turns red. When added to base, it turns blue. Available in- Solution form, Paper strips Neutral solution The solution which donot change the colour of either red or blue litmus, is known as neutral solution. Example- Sugar solution, water etc. China rose as indicator China rose indicator t...
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