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Forces in Nature

The document summarizes the fundamental forces in nature. There are four fundamental forces: gravitational force, electromagnetic force, weak nuclear force, and strong nuclear force. Gravitational force acts between all masses and depends on the product of the masses and the inverse square of the distance between them. Electromagnetic force encompasses both electrostatic and magnetic forces. The strong nuclear force binds protons and neutrons in the nucleus despite their electrostatic repulsion. The weak nuclear force is responsible for beta decay in nuclei.

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1K views3 pages

Forces in Nature

The document summarizes the fundamental forces in nature. There are four fundamental forces: gravitational force, electromagnetic force, weak nuclear force, and strong nuclear force. Gravitational force acts between all masses and depends on the product of the masses and the inverse square of the distance between them. Electromagnetic force encompasses both electrostatic and magnetic forces. The strong nuclear force binds protons and neutrons in the nucleus despite their electrostatic repulsion. The weak nuclear force is responsible for beta decay in nuclei.

Uploaded by

rajesh.v.v.k
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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F O R CE S I N N AT UR E

T h e forces are classified into two categories as fundamental and derived


forces.
The fundamental forces are
1. Gravitational force
2. Electromagnetic forces
3. Weak nuclear and strong nuclear forces.
All other forces can be derived from these fundamental forces, hence
they are called derived forces. For example, van der Waals
force(derived from the electrostatic force between the molecules), surface
tension, friction, normal forces, and so on.
!!
Fundamental Forces of Nature !
!
Gravitational Force
!
Newton discovered the universal law of gravitation, according to which the
force on a test particle ted at due to an object situated at a distance r from the
test particle is

Gm1m2
F  2
r

Where G is universal gravitational constant


G = 6.674 X 10-11Nm2Kg-2

Electro
! static and magnetic Forces:
Electro static force:
The static charges either attract or repel each other. The force of
attraction or repulsion depends on product of magnitude of two
charges and inversely proportional to the square of the distance
between them.
1 q 1q 2
F
40 r 2

This force is known as electrostatic coulomb force.


Where q1, q2 are the electric charges of the two particles separated
by distance r and ϵ0 is the permittivity of vacuum.
Electromagnetic force:
T he force between two current-carrying wires is a electro magnet force. In
the case of infinitely-long two parallel current-carrying wires, the magnitude
of the force between them is:
F 
0 II
1 2

4 r

Where I1 and I2 are the currents flowing in the two wires, and r is the
perpendicular distance between the wires.
The force on an electric charge q moving with velocity v in the magnetic
field B is
  
F  q( E  v  B)

[Note: Faraday (1831) showed that a changing magnetic field produces


an electric field, while Maxwell (1861) showed that a changing electric
field induces a magnetic field. These observations led to a unification of
electric and magnetic forces. Maxwell discovered a comprehensive set of
equations that include both electric and magnetic fields. Note that the
magnetic forces between bar magnets can be understood in terms of
microscopic currents inside the magnets. Electromagnetic waves
propagate in vacuum or medium due to the changing electric and
magnetic fields]

!
3. (i) Strong Nuclear Force: The forces among nucleons are known as Nuclear
forces. A nucleus contains protons and neutrons. The Coulomb repulsion
between the protons in a nucleus is very strong due to the short distance
between them, and it can tear apart the nucleus. Physicists discovered that
the above repulsion is surmounted by a strong attractive force between
protons and protons, protons and neutrons, and neutrons and neutrons. This
force is called strong nuclear force.
(ii) Weak Nuclear Forces: The weak nuclear force is active inside the
nucleus but it is many orders of magnitude weaker than the strong nuclear
force. This force is responsible for converting a neutron to a proton, a
process known as beta decay. An electron and a neutrino are emitted in the
process.

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