Page 139 - SCERT Kerala State Syllabus 8th Standard Basic Science Textbooks English Medium Part 1_Neat

Why are they designed in a peculiar shape? Discuss.
Don't you think this reduces the friction due to air, water or
both when they move forward?

Designing the shape of objects so as to reduce friction is
Streamlining.
Haven't you noticed oil being applied to a pulley used to draw
water from a well and oil or grease being applied in the moving
parts of vehicles. What is the advantage of doing so?
Such materials used to reduce friction are the lubricants.
Graphite is a solid lubricant.

List out other materials used as lubricants.
coconut oil

Needle bearing
Have you noticed bearings being used to reduce friction between
Fig. 10.9 (a)
the surfaces of contact of moving parts of machines? Here the
principle that rolling friction is less than sliding friction is made
use of. Are there other methods to reduce friction? Friction is
also reduced by polishing surfaces. From what you have
understood so far, state the methods adopted to reduce friction.
use lubricants.

Are you familiar with any other forces experienced in daily life?
Ball bearing
Fig. 10.9 (b) Thrust and Pressure
Did you notice the conversation?

Let's examine what it means.
See "gharshanam
kurackunna reethikal" So much to worry
in School Resources in for merely stepping
IT@ School Edubuntu Ouch! on a nail! I can
even lie on a bed
a nail…..
of nails.

138 Basic Science VIII