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Impulse




In Classical Mechanics , the ''impulse of a force'' is the product of the force and the time during which it acts. Although momentum is conserved within a closed system, individual parts of a system can undergo changes in momentum. Impulse has the same units and dimensions as momentum ( Kg M/s or N - S ). The impulse of a time-varying force is calculated as the Integral of Force with respect to Time :

:\mathbf{I} = \int \mathbf{F}\, dt
:::where
::::I is impulse,
::::F is the force,
:::: ''t'' is an Infintesimal amount of time.

In the presence of a constant Net Force , impulse is equal to the Average impulse:

:\mathbf{I} = m \Delta \mathbf{v} = \mathbf{F}\Delta t
:::where
::::''m'' is the mass of the object,
::::Δv is the change in velocity,
::::F is the ''constant'' net force applied (in order to change the velocity), and
::::\Delta t is the time interval over which the force is applied.

Using the definition of force yields:

:\mathbf{I} = \int rac{d\mathbf{p}}{dt}\, dt
:\mathbf{I} = \int d\mathbf{p}
:\mathbf{I} = \Delta \mathbf{p}

In the technical sense, impulse is a physical quantity, not an event or force. However, the term "impulse" is also used to refer to a change in an object's momentum caused by a fast-acting force. This type of impulse is often ''idealized'' so that the change in momentum happens with no change in time. This sort of change is a Step Change , and is not physically possible. However, this is a useful model for certain computations, such as computing the effects of ideal collisions, especially in game Physics Engine s.


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