Page 1 - Lesson notes- Types of force

SAI INTERNTIONAL SCHOOL
Class 8
Lesson Notes
Subject- Physics
Ch- Force and Pressure
Subtopic- Types of Force

CONTACT FORCE: Force that can be applied only by physical contact with
the object is called contact force.
Eg. Muscular force, Frictional Force

• Muscular force: The force resulting due to action of muscles.
• Friction: Force acting opposite to the direction of relative motion.

NON CONTACT FORCE: Force that can be applied without any direct or in-
direct physical contact with the object is called non contact force.
Eg. Magnetic force, Electrostatic force, Gravitational force

• Magnetic Force: Force exerted by the magnet on the magnetic
material.
o It can be attractive (between unlike poles or between magnet
and iron) or repulsive (between like poles).
o Magnetic compass works due to magnetic field of earth.
o Migratory birds use Earth’s magnetic field to navigate.
• Electrostatic Force: Force exerted by a charged body on another
charged body.
o It can be attractive (between opposite charges or between
charged and uncharged object) or repulsive (between similarly
charged objects).
o Lightning is due to electrostatic charges.
• Gravitational force: Attractive force between any two bodies having
mass.
o Gravitational force between two bodies around us is negligible
because they have small masses. But for heavenly bodies like
planets and stars, gravitational force is large because they are
huge and have much higher mass.
o Gravitational force is always attractive in nature.
o When we jump, we land back on Earth due to gravitational force.

Some More Examples of CONTACT FORCE:

Tension Force: Force exerted by a compressed or stretched spring upon any
object that is attached to it.
Example: A spring-loaded door closer.

Normal Force: The support force exerted upon an object in contact with
another stable object.