随着时间的推移施加的力会产生冲动,动量的变化。脉冲在经典力学中被定义为力乘以它作用的时间量。在微积分方面,脉冲可以计算为力相对于时间的积分。冲动的符号是J或Imp。或者,可以将脉冲计算为两个给定实例之间的动量差。 Impulse =动量变化=力x时间。力是矢量(方向重要),脉冲也是同一方向的矢量。当脉冲应用于对象时,其线性动量具有向量变化。冲动是作用于物体的平均净力及其持续时间的乘积。 J =F̅Δt平均力与其施加时间的乘积是力的推力。它等于不改变质量的物体的动量变化。冲动单位
SI的脉冲单位与动量相同,牛顿秒N * s或kg * m / s。这两个词是平等的。冲量的英制工程单位是磅 – 秒(lbf * s)和每秒slu-foot(slug * ft / s)。冲动 – 动量定理
该定理在逻辑上等同于牛顿第二运动定律:力等于质量乘以加速度,也称为力定律。物体动量的变化等于施加于它的冲动。 J =Δp。该定理可以应用于恒定质量或变化质量。它特别适用于火箭,火箭的质量随着燃料的消耗而变化而产生推力。在研究冲击力时,这是一个有用的概念。如果增加力的变化发生的时间,冲击力也会减小。这用于机械设计以确保安全,并且在运动应用中也很有用。您希望减少汽车撞击护栏的冲击力,例如,通过设计护栏以折叠以及设计汽车部件以在撞击时揉皱。这延长了撞击的时间,从而延长了力。如果你想要进一步推进球,你需要用球拍或球棒缩短撞击时间,提高冲击力。与此同时,拳击手知道远离拳击,因此着陆需要更长时间,从而减少了影响。比冲是衡量火箭和喷气发动机效率的指标。它是一个推进剂单位在消耗时产生的总冲量。如果火箭具有更高的比冲,则需要更少的推进剂来获得高度,距离和速度。它相当于推力除以推进剂流量。如果使用推进剂重量(牛顿或磅),则以秒为单位测量特定脉冲。这通常是制造商报告火箭发动机性能的方式。

美国南加州大学物理学Assignment代写:随着时间推移的力量

Force applied over time creates an impulse, a change in momentum. Impulse is defined in classical mechanics as a force multiplied by the amount of time it acts over. In calculus terms, the impulse can be calculated as the integral of force with respect to time. The symbol for impulse is J or Imp. Alternately, impulse can be calculated as the difference in momentum between two given instances. Impulse = change in momentum = force x time. Force is a vector quantity (the direction matters) and impulse is also a vector in the same direction. When an impulse is applied to an object, it has a vector change in its linear momentum. Impulse is the product of the average net force acting on an object and its duration. J = F̅Δt The product of average force and the time in which it is exerted is the impulse of force. It is equal to the change of momentum of an object that isn’t changing mass. Units of Impulse. The SI unit of impulse is the same as for momentum, the newton second N*s or kg*m/s. The two terms are equal. English engineering units for impulse are pound-second (lbf*s) and slug-foot per second (slug*ft/s). The Impulse-Momentum Theorem. This theorem is logically equivalent to Newton’s second law of motion: force equals mass times acceleration, also known as the force law. The change in momentum of an object equals the impulse applied to it. J = Δ p. This theorem can be applied to a constant mass or to a changing mass. It is relevant especially to rockets, where the mass of the rocket changes as fuel is expended to produce the thrust. This is a useful concept when you are studying impact forces. If you increase the time over which the change of force happens, the impact force also decreases. This is used in mechanical design for safety, and it is useful in sports applications as well. You want to reduce the impact force for a car hitting guardrail, for example, by designing the guardrail to collapse as well as designing parts of the car to crumple on impact. This lengthens the time of the impact and therefore the force. If you want a ball to be propelled further, you want to shorten the time of impact with a racket or bat, raising the impact force. Meanwhile, a boxer knows to lean away from a punch so it takes longer in landing, reducing the impact. Specific impulse is a measure of the efficiency of rockets and jet engines. It is the total impulse that is produced by a unit of propellant as it is consumed. If a rocket has a higher specific impulse, it needs less propellant to gain altitude, distance, and speed. It is the equivalent of the thrust divided by the propellant flow rate. If the propellant weight is used (in newton or pound), specific impulse is measured in seconds. This is often how rocket engine performance is reported by manufacturers.

发表评论

电子邮件地址不会被公开。 必填项已用*标注