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:

Impulse is the force applied in a unit of time. force x time which equates to change in momentum.

$\backslash mathbf\{I\}\; =\; \backslash int\; \backslash mathbf\{F\}\backslash ,\; dt$

I is impulse,

F is the force,

dt is an infinitesimal amount of time.

In the presence of a constant net force, impulse is equal to the average impulse:

$\backslash mathbf\{I\}\; =\; m\; \backslash Delta\; \backslash mathbf\{v\}\; =\; \backslash mathbf\{F\}\backslash Delta\; t$

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

$\backslash Delta\; t$ is the time interval over which the force is applied.

Using the definition of force yields:

$\backslash mathbf\{I\}\; =\; \backslash int\; \backslash frac\{d\backslash mathbf\{p\}\}\{dt\}\backslash ,\; dt$

$\backslash mathbf\{I\}\; =\; \backslash int\; d\backslash mathbf\{p\}$

$\backslash mathbf\{I\}\; =\; \backslash Delta\; \backslash mathbf\{p\}$

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 engines.

See also

• specific impulse
• Wave-particle duality defines an impulse for waves. The preservation of momentum at a collision is then called phase matching. Applications include:
  • Compton effect
  • nonlinear optics
  • Acousto-optic modulator
  • Umklapp scattering
  • electron phonon scattering

References

External links and references

• Dynamics

Physical quantity | Classical mechanics

Impuls (fysik) | Impuls (Mechanik) | Impuls sile | 力積 | Impuls | Popęd (fizyka) | Impulssi