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Answers
1. Advantages of friction:
1. Friction enables us to walk freely.
2. It helps to support ladder against wall.
3. It becomes possible to transfer one form of energy to another.
4. Objects can be piled up without slipping.
5. Breaks of vehicles work due to friction.
Disadvantages of friction:
1.It always resists the motion, so extra energy is required to overcome it.
2.It causes wear and tear of machines.
3.It decreases the life expectancy of moving parts of vehicles.
4.Since friction is very useful in some cases while harmful in some cases, friction is called a necessary evil.
2. Rolling friction takes place when an object rolls on the surface. Sliding friction takes place when two surfaces are rubbed against each other. Rolling friction takes place due to the deformation of surfaces.
3. Board pins are made sharp as they can easily penetrate the surface of the soft board .
4. That pressure is called atmospheric pressure, or air pressure. It is the force exerted on a surface by the air above it as gravity pulls it to Earth. Atmospheric pressure is commonly measured with a barometer. ... One atmosphere is 1,013 millibars, or 760 millimeters (29.92 inches) of mercury.
Explanation
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