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Force:
Force is an external effort in the form of push or pull.
- It produces or tries to initiates the motion of a static body.
- It stops or tries to stop a moving body.
- It changes or tries to change the direction of motion of a moving body.
Force has both magnitude and direction. So, it is a vector quantity.
Units of force:
The SI unit of force is newton (\(N\)), and in the C.G.S. system, its unit is dyne.
\(1\ N\)\(ewton\) (\(N\)):
The amount of force needed for a body of mass \(1\ kg\) produces an acceleration of \(1\) ,
\(1\) \(N\) \(=\) \(1\) \(kg\)
\(1\ dyne\):
The amount of force needed for a body of mass \(1\ gram\) produces an acceleration of \(1\) ,
\(1\) \(dyne\) \(=\) \(1\ g\) , also
\(1\) \(N\) \(=\) \(10^5\) \(dyne\)
Unit force:
The amount of force needed to produce an acceleration of \(1\) in a body of mass \(1\) \(kg\) is known as ‘unit force’.
Gravitational unit of force:
In the S.I. system of units, the gravitational unit of force is kilogram-force, represented by \(kg f\). In the C.G.S. system, its unit is \(gram force\), represented by \(g f\).
\(1\) \(kg f\) \(=\) \(1\) \(kg \times 9.8\) \(m s^{-2}\) \(=\) \(9.8\) \(N\)
\(1\) \(g f\) \(=\) \(1\) \(g \times 980\) \(cm s^{-2}\) \(=\) \(980\) \(dyne\)
\(1\) \(kg f\) \(=\) \(1000\) \(g \times 980\) \(cm s^{-2}\) \(=\) \(980 \times 10^{3}\) \(dyne\)
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