Unit of Force – Class 11 | Chapter – 2 | Physics Short Notes Series PDF for NEET & JEE

Unit of Force: The unit of force is the newton (N), named after Sir Isaac Newton, a prominent physicist and mathematician. One newton is defined as the amount of force required to give a mass of one kilogram an acceleration of one meter per second squared. Another commonly used unit of force is the pound-force (lbf), which is defined as the force required to accelerate a mass of one pound at a rate of 32.17405 feet per second squared (approximately 9.80665 m/s²). However, the newton is the standard unit of force in the International System of Units (SI).

Unit of Force

Force is described by Newton’s laws of motion, which state that an object will remain at rest or continue to move at a constant velocity unless acted upon by a force. The second law of motion describes how the force acting on an object affects its acceleration. It states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass, force can be mathematically represented as:

Force (F) = mass (m) x acceleration (a)

This can be expressed as F = mass x (length/time²) in terms of the seven fundamental dimensions of the physical world.

The dimensional formula for force can be written as: F = [M][L]/[T²]

= [M L T^-2]

SI Unit of Force

SI Unit of Force, Newton is the universally accepted system of measurement. The SI Unit of force is denoted by the letter N written in uppercase. Mathematically this can be represented from Newton’s second law of motion as:

F= ma

 

Derivation of SI Unit of Force

From Netwon’s second law, force (F) is the rate of change of momentum (P). The momentum is a product of mass (m) and velocity (v). Therefore, 

Force = Rate of change of Momentum

= P/t, where t is the time

Substituting for momentum we get, 

F = mv/t

Substituting for units we get

N= kg. m/s.s

= kgm/s²

Here,

• unit of force= N= kg/ms²
• unit of mass = kg
• unit of velocity = m/s
• unit of time = s

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By Team Learning Mantras