AskDefine | Define impulse

Dictionary Definition



1 an instinctive motive; "profound religious impulses" [syn: urge]
2 a sudden desire; "he bought it on an impulse" [syn: caprice, whim]
3 the electrical discharge that travels along a nerve fiber; "they demonstrated the transmission of impulses from the cortex to the hypothalamus" [syn: nerve impulse]
4 (electronics) a sharp transient wave in the normal electrical state (or a series of such transients); "the pulsations seemed to be coming from a star" [syn: pulsation, pulsing, pulse]
5 the act of applying force suddenly; "the impulse knocked him over" [syn: impulsion, impetus]
6 an impelling force or strength; "the car's momentum carried it off the road" [syn: momentum]

User Contributed Dictionary




From impulsus.


  1. A wish or urge, particularly a sudden one.
    The impulse to learn drove me to study night and day.
    When I saw the new dictionary, I couldn't resist the impulse to browse through it.
  2. The integral of force over time.
    The total impulse from the impact will depend on the kinetic energy of the bullet.



Century 1911}}




Extensive Definition

In classical mechanics, an impulse is defined as the integral of a force with respect to time:
\mathbf = \int \mathbf\, dt
I is impulse (sometimes marked J),
F is the force, and
dt is an infinitesimal amount of time.
A simple derivation using Newton's second law yields:
\mathbf = \int \frac\, dt
\mathbf = \int d\mathbf
\mathbf = \Delta \mathbf
This is often called the impulse-momentum theorem.
As a result, an impulse may also be regarded as the change in momentum of an object to which a force is applied. The impulse may be expressed in a simpler form when both the force and the mass are constant:
\mathbf = \mathbf\Delta t = m \Delta \mathbf = \Delta\ p
F is the constant total net force applied,
\Delta t is the time interval over which the force is applied,
m is the constant mass of the object,
Δv is the change in velocity produced by the force in the considered time interval, and
mΔv = Δ(mv) is the change in linear momentum.
However, it is often the case that one or both of these two quantities vary.
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 fast-acting force. This type of impulse is often idealized so that the change in momentum produced by the force 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 purposes, such as computing the effects of ideal collisions, especially in game physics engines.
Impulse has the same units and dimensions as momentum (kg m/s = N·s).
Using basic math, Impulse can be calculated using the equation:
\mathbft = \Delta\ p
\Delta\ p can be calculated, if initial and final velocities are known, by using "mv(f) - mv(i)" or otherwise known as "mv - mu"
F is the constant total net force applied,
t is the time interval over which the force is applied,
m is the constant mass of the object,
v is the final velocity of the object at the end of the time interval, and
u is the initial velocity of the object when the time interval begins.
Hence: \mathbft = mv - mu

See also



  • Physics for Scientists and Engineers
  • Physics for Scientists and Engineers: Mechanics, Oscillations and Waves, Thermodynamics

External links and references

impulse in Czech: Impuls síly
impulse in Danish: Impuls (fysik)
impulse in German: Kraftstoß
impulse in Croatian: Impuls sile
impulse in Italian: Impulso (fisica)
impulse in Malay (macrolanguage): Impuls
impulse in Dutch: Stoot
impulse in Japanese: 力積
impulse in Polish: Popęd (fizyka)
impulse in Finnish: Impulssi
impulse in Turkmen: Impuls
impulse in Ukrainian: Імпульс сили
impulse in Chinese: 冲量

Synonyms, Antonyms and Related Words

actuation, archetypal pattern, archetype, atomic power, automatic writing, automatism, blind impulse, catalyst, collective unconscious, compulsion, compulsiveness, conditioning, constraint, drive, echolalia, echopraxia, electric power, electropower, excitant, exigency, forwardness, goad, haste, hastiness, horsepower, hydraulic power, hydroelectric power, id, impetus, impulsion, impulsiveness, inborn proclivity, incentive, incitation, incitement, instinct, instinctiveness, involuntariness, jet power, libido, lust, manpower, motivation, natural instinct, natural tendency, nuclear power, overhastiness, passion, pinch, piston power, precipitation, precociousness, precocity, prematureness, prematurity, press, pressure, primitive self, propulsion, push, rash impulse, reflex action, rocket power, rush, sheer chemistry, solar power, spur, steam power, stimulant, stress, subconscious urge, thermonuclear power, thrust, unlearned capacity, unreasoning impulse, untimeliness, unwilledness, urge, urgency, vital impulse, water power
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