Page 1 - Lesson notes -Methods to increase and decrease friction

SAI INTERNATIONAL SCHOOL
Class 8
Lesson Notes
Subject-Physics
CH-Friction
Subtopic-Methods to Increase and Decrease friction

Methods to increase friction:
1. Make the surface rough: Grooves are made in the shoe soles to increase friction.
Gymnast apply some coarse substance on their hands to increase friction.
2. Press the surfaces harder against each other: while walking on a slippery surface,
we need to place our feet carefully and press it hard against the floor to avoid
slipping.

Methods to decrease Friction:
1. By making surface smooth: The slides in the park are polished to make it smooth
and easy to slide.
2. By applying lubricants: Oil is poured in the machines to reduce friction.
3. By using wheels/ ball bearings: Wheels are provided in suitcase to reduce friction
while pulling. Ball bearings are used between machine parts which slide over each
other to reduce friction.

Note:
Lubricant is a substance which is used between the surfaces of the moving objects to
reduce friction.
n They reduce friction by filling up the irregularities and making a thin layer
between the surface. Thus, preventing the interlocking of irregularities.
n Eg: oil, grease, graphite powder

Activity: Marble Slide Friction Experiment

Objective:
Demonstrate how different materials affect the movement of a marble.

Materials:
Round cake pan, Marble, Various materials to line the pan (e.g., fabric, foil, sandpaper)

Procedure:
• Place the marble at the center of the cake pan.
• Tilt the pan to create a slope and observe how the marble moves.