CHAPTER : FRICTION 8 STD CBSE SCIENCE SYLLABUS.

1. If you apply the
force along the right,
the friction acts
along the left
direction. In both
cases the force
opposes the motion
CHAPTER :FRICTION
CBSE

2. Griffin Educare
Friction is caused by the irregularities on the two
surfaces in contact
Irregularities on the two surfaces lock into one
another. When we attempt to move any surface,
we have to apply a force to overcome
interlocking. On rough surfaces, there are a
larger number of irregularities. So the force of
friction is greater if a rough surface is involved.

3. It is obvious that the force of friction will
increase if the two surfaces are pressed harder.
You can experience it by dragging a mat when
nobody is sitting on it, and when a preson is
sitting on it.

4. Factors affecting friction
1. Roughness of the surface.
2. The amount of pressure applied to pull the object

5. • Cause of friction
• Friction is caused due to interlocking of
irregularities between the two surface in contact
• Smooth surfaces have minute irregularities
between the two surfaces
• Rough surfaces have larger irregularities between
the 2 surfaces
• So force of friction is more if the surface are rough

6. Types of friction

7. • Static friction is the friction exerted on
an object at rest
• Sliding friction is the friction exerted
when an object slides over a surface
• Rolling friction is the friction exerted
when an object rolls over a surface
• Sliding friction is less than static
friction rolling friction is less than
static friction

8. Increasing friction
• Friction can be increased by increasing the
roughness of the surface in contact
• Example the soul of shoes are groove to have a
better grip on the floor
• The brake pads of vehicle are rough to stop moving
vehicle when the brakes are applied
• The tyres of vehicle are traded to increase the grip
on the road

9. Reducing friction
• Friction can be reduced by
• Using lubricants like powder or oils and grease
• Using rollers or wheels
• We sprinkle powder on a boat to reduce friction
• Oil of grease is applied between moving parts of
machine reduces friction