![]() When a projectile is sent on a very long journey, as is the case with ICBMs, the magnitude and direction of the acceleration due to gravity changes. The wide geographic range as well as the wide historic range of these things we call projectiles raises some problems for the typical student of physics. ICBMs are the ultimate killing machines, but they have never been used in combat to date. The adjective "intercontinental" refers to the long range capabilities, while the largely free fall journey it takes makes it "ballistic". At the start of its journey an ICBM is guided by a rocket engine and stabilizer fins, but soon thereafter it enters the phase of its journey where it is effectively in free fall, traveling fast enough to keep it above Earth's atmosphere for a while but not fast enough to enter orbit permanently. An intercontinental ballistic missile is a device for delivering nuclear warheads over long distances.Before the invention of gunpowder, ballistas (and catapults and trêbuchets) were the weapons of choice for conquerors. The ballista, which looks something like a giant crossbow, was a siege engine used in medieval times to hurl large stones, flaming bundles, infected animal carcasses, and severed human heads into fortifications.The word ballistic has its origins in the Greek word βαλλω ( vallo), to throw, and surfaces repeatedly in the technical jargon of weaponry from ancient to modern times. To get around this dilemma, it is common to use the term ballistic trajectory when dealing with projectiles. Since these devices are acted upon by the lift of wings and the thrust of engines in addition to the force of gravity, they are not really projectiles. Airplanes, guided missiles, and rocket-propelled spacecraft are sometimes also said to follow a trajectory. This is where we run into some linguistic complications. The only relevant quantities that might vary from projectile to projectile then are initial velocity and initial position The trajectory of a projectile is thus entirely determined the moment it satisfies the definition of a projectile. An object ceases to be a projectile once any real effect is made to change its trajectory. Of course, the pilot of a disabled airplane may regain control before crashing and avert disaster, but then the airplane wouldn't be a projectile anymore. No amount of leaning to one side will make a foul ball turn fair. Batters may apply "body English" after hitting a long ball, but they do so strictly for psychological reasons. A projectile is any object with an initial non-zero, horizontal velocity whose acceleration is due to gravity alone.Īn essential characteristic of a projectile is that its future has already been preordained. ![]() The normal amounts of drag and buoyancy just aren't large enough to save the passengers on a doomed flight from an unfortunate end. Even though the drag and buoyant forces acting on it are much greater in absolute terms than they are on the balloon, gravity is what really drives a crashing airplane. In contrast, a crashing airplane would be considered a projectile. Helium-filled balloons can't be thrown long distances and don't normally fall. A tossed helium-filled balloon is not normally considered a projectile as the drag and buoyant forces on it are as significant as the weight. This is not to say that other forces do not exist, just that their effect is minimal in comparison. The force of primary importance acting on a projectile is gravity. the space shuttle or any other spacecraft after main engine cut off (MECO).a runner in mid stride (since they momentarily lose contact with the ground).a moving airplane in the air with its engines and wings disabled.a bullet the instant it exits the barrel of a gun or rifle.a baseball that has been pitched, batted, or thrown.(This is an informal definition.) The path of a projectile is called its trajectory. A projectile is any object that is cast, fired, flung, heaved, hurled, pitched, tossed, or thrown.
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