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A large force that acts on a body for a very short period of time is called an 'Impulsive force'.

When a force '\(F\)' acts on a body for a duration of time '\(t\)', then the product of force and time period is called 'impulse', represented by '\(J\).'

$\mathit{Impulse}(J)\; =\mathit{Force}\phantom{\rule{0.147em}{0ex}}(F)\phantom{\rule{0.147em}{0ex}}\times \mathit{Time}\phantom{\rule{0.147em}{0ex}}(t)\phantom{\rule{0.147em}{0ex}}...\phantom{\rule{0.147em}{0ex}}\mathit{eqn}\phantom{\rule{0.147em}{0ex}}(1)$

By Newton's second law,

$\begin{array}{l}\mathit{Force}\phantom{\rule{0.147em}{0ex}}(F)\; =\frac{\mathit{Change}\phantom{\rule{0.147em}{0ex}}\mathit{in}\phantom{\rule{0.147em}{0ex}}\mathit{momentum}\phantom{\rule{0.147em}{0ex}}(\mathrm{\Delta}p)}{\mathit{time}\phantom{\rule{0.147em}{0ex}}(t)}(\Delta \mathit{refers}\mathit{to}\mathit{change})\\ \\ \mathrm{\Delta}p\phantom{\rule{0.147em}{0ex}}=\phantom{\rule{0.147em}{0ex}}F\phantom{\rule{0.147em}{0ex}}\times \phantom{\rule{0.147em}{0ex}}t\phantom{\rule{0.147em}{0ex}}...\phantom{\rule{0.147em}{0ex}}\mathit{eqn}\phantom{\rule{0.147em}{0ex}}(2)\end{array}$

From equations (1) and (2)

$J=\mathrm{\Delta}p$

Impulse is also equal to the magnitude of change in momentum.

The SI unit of impulse is the \(newton-second\) (\(Ns\)) and the dimensionally equivalent unit of momentum is the \(kilogram\ meter\ per\ second\) ($\mathit{kgm}{s}^{-1}$).

Change in momentum can be attained in two ways. They are:

**a large force acting for a short duration of time, and****a smaller force acting for a longer duration of time.**

**Examples**:

- Automobiles are furnished with springs and shock absorbers to decrease jerks while moving on rough roads.

- In cricket, while catching the ball, a fielder pulls back his hands. He experiences a smaller amount of force for a longer period of time to catch the ball, resulting in a much lesser impulse on his hands.

Reference:

https://commons.wikimedia.org/wiki/File:Andrew_Hodd,_Sussex_Wicketkeeper.jpg