Friction is the force that opposes the motion of objects in contact with one another. It slows down moving objects and causes them to stop. The amount of friction depends on how rough or smooth the surfaces in contact are. Rough surfaces have more friction while smooth surfaces have less. Friction is both advantageous and disadvantageous. It enables movement like walking but also causes wear and reduces efficiency. Methods to reduce friction include lubrication and smoothing surfaces, while increasing surface roughness adds friction.

1. Friction
Prepared by:
HARSH
8THA4
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3. Friction
• Force that opposes the motion of an
object when the object is in contact
with another object or surface.
• Force that slows down or stops
motion.

4. How FRICTION affects motion?
 if you roll a ball along the floor or ground, it
will slow down and stop even though no
apparent force is being applied to it. The
ball slows down and stops because of
friction.
 Friction slows down a moving object.
Friction occurs when two objects rub
against each other.

5.  A car that runs on a very rough roadA car that runs on a very rough road
slows down due to friction. However, onslows down due to friction. However, on
a smooth road, it travels fast.a smooth road, it travels fast.
 A smooth surface has a very few bumpsA smooth surface has a very few bumps
and hollows. There is less friction on aand hollows. There is less friction on a
smooth surface. A running object cansmooth surface. A running object can
glide or move continuously with veryglide or move continuously with very
little force.little force.

6.  Smooth surface produces less friction
and allows shoes and tires to slip.
 On a rough surface, there are more
bumps and hollows. When you push the
cart on a rough road, it will travel slowly.
There’s more friction acting on the moving
cart. The rougher the surface, the more
friction there is, thus, the slower an object
moves.

7.  Friction is lesser on a smooth,Friction is lesser on a smooth,
shiny surface.shiny surface.
 Friction is greater on a roughFriction is greater on a rough
surface.surface.

8. Advantages and Disadvantages ofAdvantages and Disadvantages of
FrictionFriction
AdvantagesAdvantages
Friction enables belts to cling toFriction enables belts to cling to
pulleys and nails to hold objectspulleys and nails to hold objects
togethertogether..

9. A running car or bicycle uses friction toA running car or bicycle uses friction to
stop. As the driver steps on the brakes,stop. As the driver steps on the brakes,
the vehicle slows down to a full stop. Thisthe vehicle slows down to a full stop. This
is possible because of the friction betweenis possible because of the friction between
the brakes and the wheels.the brakes and the wheels.

10. Walking, running, playing, writing, sitting,Walking, running, playing, writing, sitting,
standing, or eating cannot be possiblestanding, or eating cannot be possible
without friction.without friction.

12. Disadvantages of Friction
 Shoes, slippers, tires and anything that are
used for moving become worn out. Friction
produces heat that causes objects to wear
out.

13.  Friction makes work tedious. Because ofFriction makes work tedious. Because of
the resistance, workers need to exertthe resistance, workers need to exert
more effort and energy to accomplish theirmore effort and energy to accomplish their
work to overcome resistance.work to overcome resistance.

14.  Some machines perform less efficiently
and wear out faster with friction.
 Friction also causes sparks, overheating,
and machine breakdown.
 Friction reduces speed. Even airplanes
cannot fly as fast as they are able
because of air friction.
 Racing cars and other vehicles consume
more energy to run fast and overcome the
resistance of the roads.

15.  Friction can also make speeding objectsFriction can also make speeding objects
to tumble down and cause accidents.to tumble down and cause accidents.

16. Ways of reducing friction
 Smoothing out Surface
ex. Applying floor wax and
scrubbing the floor.
 Placing a slippery substances
between two solid surfaces
ex. Grease, oil and other
lubricating liquids

17.  Using rotating objectsUsing rotating objects
ex. Roller bearings, ball bearings andex. Roller bearings, ball bearings and
wheelswheels

18.  Streamlining vehicles to reduce friction causedStreamlining vehicles to reduce friction caused
by air.by air.
ex. Streamlined front of planesex. Streamlined front of planes

19. Ways to increase frictionWays to increase friction
 New materials with more bumps and hollowsNew materials with more bumps and hollows
are produce for making car brakes lining.are produce for making car brakes lining.

20.  New styles for the soles of athletes’New styles for the soles of athletes’
shoes. Its aim is for runners to run withshoes. Its aim is for runners to run with
greater speed.greater speed.

21. Write the letter of the best answer.
1. It is the force that slows down or
stops motion.
a. Acceleration b. motion
b. friction
2. Friction is always beneficial.
a. True b. false
3. Friction can be reduced.
a. True b. false

22. • 4. What is the effect of spikes on
the shoes of a runner?
• A. Increase his speed
• B. Increase friction
• C. all
• 5. How will you decrease friction?
• A. Apply lubricant
• B. Polish surface
• C. all