In classical mechanics, impulse (symbolized by J or Imp) is the change in momentum of an object. If the initial momentum of an object is p1, and a subsequent momentum is p2, the object has received an impulse J:
Momentum is a vector quantity, so impulse is also a vector quantity:Newton's second law of motion states that the rate of change of momentum of an object is equal to the resultant force F acting on the object:so the impulse J delivered by a steady force F acting for time Δt is:
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A sledgehammer is a tool with a large, flat, massive, often metal head, attached to a long wooden or solid handle. The long handle is combined with a heavy head which allows the sledgehammer to pick up momentum during a swing and apply a large force compared to hammers designed to drive nails. Along with the mallet, it shares the ability to distribute force over a wide area. This is in contrast to other types of hammers, which concentrate gravity and force in a relatively small area.
Delta-v (also known as "change in velocity"), symbolized as and pronounced /dɛltə viː/, as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or landing on a planet or moon, or an in-space orbital maneuver. It is a scalar that has the units of speed. As used in this context, it is not the same as the physical change in velocity of said spacecraft.
A simple example might be the case of a conventional rocket-propelled spacecraft, which achieves thrust by burning fuel. Such a spacecraft's delta-v, then, would be the change in velocity that spacecraft can achieve by burning its entire fuel load.
A contact force is any force that occurs because of two objects making contact with each other. Contact forces are very common and are responsible for most visible interactions between macroscopic collections of matter. Pushing a car or kicking a ball are everyday examples where contact forces are at work. In the first case the force is continuously applied to the car by a person, while in the second case the force is delivered in a short impulse.
Contact forces are often decomposed into orthogonal components, one perpendicular to the surface(s) in contact called the normal force, and one parallel to the surface(s) in contact, called the friction force.
Recoil (often called knockback, kickback or simply kick) is the rearward thrust generated when a gun is being discharged. In technical terms, the recoil is a result of conservation of momentum, for according to Newton's third law the force required to accelerate something will evoke an equal but opposite reactional force, which means the forward momentum gained by the projectile and exhaust gases (ejectae) will be mathematically balanced out by an equal and opposite impulse exerted back upon the gun.
Specific impulse (usually abbreviated as Isp) is a measure of how efficiently an engine, such as a rocket or jet engine generates thrust. It is either measured in units of velocity (metres per second, or feet per second), or time (seconds). When measured in velocity, this is the effective exhaust velocity used in the Tsiolkovsky rocket equation which calculates how much an engine with a given quantity of fuel can change a vehicle's velocity. When measured as a time, Isp is the velocity divided by earth's gravity, g. This is convenient because the time is the same in metric and English units. This is the time that one kilogram of fuel can produce one kilogram of thrust, which is equal to the time that one pound of fuel can produce one pound of thrust.
Specific impulse is a ratio of the impulse, i.e. change in momentum, to the mass of propellant. This is equivalent to "thrust per massflow".
A kinetic energy weapon (also known as kinetic weapon, kinetic energy warhead, kinetic warhead, kinetic projectile, kinetic kill vehicle) is a projectile weapon based solely on a projectile's kinetic energy to inflict damage to a target, instead of using any explosive, incendiary, chemical or radiological payload. All kinetic weapons work by attaining a high flight speed – generally supersonic or even up to hypervelocity – and collide with their targets, converting their kinetic energy and relative impulse into destructive shock waves, heat and cavitation. In kinetic weapons with unpowered flight, the muzzle velocity or launch velocity often determines the effective range and potential damage of the kinetic projectile.
Kinetic weapons are the oldest and most common ranged weapons used in human history, with the projectiles varying from blunt projectiles such as rocks and round shots, pointed missiles such as arrows, bolts, darts, and javelins, to modern tapered high-velocity impactors such as bullets, flechettes, and penetrators. Typical kinetic weapons accelerate their projectiles mechanically (by muscle power, mechanical advantage devices, elastic energy or pneumatics) or chemically (by propellant combustion, as with firearms), but newer technologies are enabling the development of potential weapons using electromagnetically launched projectiles, such as railguns, coilguns and mass drivers. There are also concept weapons that are accelerated by gravity, as in the case of kinetic bombardment weapons designed for space warfare.
The newton-second (also newton second; symbol: N⋅s or N s) is the unit of impulse in the International System of Units (SI). It is dimensionally equivalent to the momentum unit kilogram-metre per second (kg⋅m/s). One newton-second corresponds to a one-newton force applied for one second.
It can be used to identify the resultant velocity of a mass if a force accelerates the mass for a specific time interval.
