FORCE

MODULE-2

DON BOSCO SCHOOL, BERHAMPORE

CLASS -6

SUBJECT- PHYSICS

FORCE OF FRICTION

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Friction exists, whenever any two objects are in contact with each other

and one object moves over the surface of the other object.

INFO HUB : Objects having more mass causes them to be pulled harder

because of gravity of the Earth. Hence, it would be difficult to move a

heavier object than a lighter object when friction comes into play.

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Some of the examples of day-to-day life are:

PROPERTIES OF FRICTION • Friction is a force that always acts whenever any two surfaces come

in contact and one surface moves or slides over the other.

• The force of friction always opposes the motion.

• Different solids experience different amounts of friction on a

surface.

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• Solids, liquids and gases all exerts the force of friction on an moving

object over or through it.

• The force of friction generates heat.

• Friction can also lead to wear and tear of the objects.

CAUSES OF FRICTION

Go through the Action Time2 on pg-49

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TYPES OF FRICTION

• It can adjust its magnitude against the applied force so it is also

known as self-adjusting force.

• It also prevents objects from slipping or skidding.

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NOTE:

• Static friction is the maximum value of friction out of the three.

• Rolling friction offers less resistance or opposition to motion than

sliding friction.

Go through ACTION TIME 3 from textbook pg-51.

FRICTION IS A NECESSARY EVIL Advantages of friction

1.It becomes difficult to walk on a slippery road due to low friction. When we move on ice,

it becomes difficult to walk due to low friction of ice.

2. We can not fix nail in the wood or wall if there is no friction. It is friction which holds the nail.

3. A horse can not pull a cart unless friction furnishes him a secure Foothold.

4. We can write on a paper or on a board.

5. Friction helps in applying the brakes.

6. It helps in walking on floor.

7. Coffee mug stays on the dashboard

8. Shuffling across a carpet to shock someone

9. We can light a matchstick.

10. Helps to protect the life on earth by burning asteroids.

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Disadvantages of friction

Despite the fact that the friction is very important in our daily life, it also has some disadvantages

like:

1. The main disadvantage of friction is that it produces heat in various parts of machines. In this

way some useful energy is wasted as heat energy.

2. Due to friction we have to exert more power in machines.

3. It opposes the motion.

4. Due to friction, noise is also produced in machines.

5. Due to friction, engines of automobiles consume more fuel which is a money loss.

6. Machine efficiency is decreased: energy input is lost to heat.

7. Getting shocked by doorknobs.

8. Rug burn.

9. It counteracts movement and so it takes more energy to move, it can cause unwanted heat (e.g. in

machine parts), and it wears things out like shoes.

10. Forest fires are caused due to friction between branches of trees.

ASSIGNMENT

Solve quick check 2 on pg-49 & objective type questions of the back

exercise on pg-53, 54 & 55.

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BY – SUPRITY YADAV & RITUPARNA CHAKRABORTY

DATE- 19-05-2020