Answer the following questions in brief.
a) Why does friction occur?
b) State the factors on which friction depends.
c) Differentiate between sliding friction and rolling friction.
d) Give a situation where we increase friction.
e) List any two disadvantages of friction.
Answers
answer
a)Friction occurs because no surface is perfectly smooth. Rougher surfaces have more friction between them. Heavier objects also have more friction because they press together with greater force. Friction produces heat because it causes the molecules on rubbing surfaces to move faster and have more energy.
b)he friction force depends on two factors:
1....... The materials that are in contact. The two materials and the nature of their surfaces. ...
2......The force pushing the two surfaces together. Pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other.
c)The main difference between sliding and rolling friction is that the sliding friction occurs when one surface is rubbing against another surface, whereas rolling friction occurs when an object is rolling on another surface.
d)we increase friction in tractors , big things
e)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.
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Answer:
a) friction accurs due to surface irregularities of two object is contact
B) friction depent on nature of surface in contact and mass of body .