Without mincing words,our knowledge of motion may never be complete without a mention of projectile motion.Eventhough motion may be translational,rotational,vibrational,or deformational,projectile motion belong more to the group of translational motion.Everywhere you go,everywhere you look,everywhere you stand,there is one or more examples of projectile motion to sniff.In a nutshell,projectile motion is a type of motion that is established whenever you throw an object horizontally or at an angle.But watch it,throwing an object vertically up or down will result in motion,but definitely,not a projectile kind.
Have you ever handle a shotgun?Have you ever tried to pull the trigger in any way?The shotgun or any other type whatsoever is designed to operate upon the basic principle of projectile motion.Once the shots are loaded into the barrel,they automatically become the object for projectile motion.Assuming the observer is a hunter in the wood scouting for whitetails,he tries to aim at a deer somewhere ahead.Once he is ready for action,a hard pull on the trigger sets off the bullet in the direction of the target or the deer.The bullet travels with a lot of energy horizontally or at an angle to hit the deer.If he does his calculation right,usually an approximate method based on experience,the bullet hits the deer and the animal lay dead in a twinkling of an eye.
The catapult is another mechanical machine whose operation is based on projectile motion.Used by teenagers and older people mainly for hunting arboreal(or tree-living)species of animals,most especially birds,it represent a more perfect tool to describe projectile motion.The object to be set in motion is usually a small piece of stone or metal bob.The trigger system,usually an elastic rubber material,is hooked on either side of the “V” of a
Y-shaped stick to provide the required strength and force to the stone whenever the trigger is pulled.How then does the observer respond to a bird at sight?Aiming correctly at the bird is the most important step.Then,he puts the object inside the fold of the elastic rubber,draw the rubber(with the stone inside) as far behind as he could,and release with the maximum possible drive or momentum.The motion of the stone from the point of release to the point at which it hits the bird is a projectile motion.
The field of astronomy offers another big picture as far as projectile motion is concerned.Our world,the earth is now known to have a spherical shape,more properly described as geoid.According to astronomers,the earth and other eight planets that made up our solar system,are constantly orbiting(or moving in a well-defined pathway)the sun.This motion of the planets in orbits around the sun is another perfect example of a projectile motion.And in a way,it shows that this motion is helpful to mankind in the sustainance of the earth and universe.
Projectile motion has been studied extensively by scientists and physicists all over the world.So,depending on the way the motion was started,it is conventional to divide a projectile motion into sections,as the overall motion is usually observed to be a combination of several smaller motions,each guided by a specific Newton’s law of motion,may be first,second,or third law.As far as projectile motion is concerned,the important parameters include:
-initial velocity(u)
-acceleration(a)
-time(t)
-final velocity(v)
-distance travelled(s)
The three equations of motion according to Newton are given below:
1. v = u + a.t
2. s = u.t + 2.a.s
3. v.v = u.u + 2.a.s
where the dot the equations represent multiplication,v.v and u.u should interpreted as v squared and u squared respectively.Every projectile motion of an object has an initial or starting velocity(or speed)and will terminate at rest,that is,with a final velocity equal to zero.With these clues,any desired and unknown parameter or value could be calculated.Such a calculation usually form the basis of design in shotguns,machine guns,bow and arrows,and other similar devises.
Lastly,understanding projectile motion is far easy now more ever before as these are a whole lot of examples around us,including shotgun,catapult,bow and arrow,and the orbiting planets around the sun.As a type of motion that is established when an object is thrown horizontally or at an angle,the principle of projectile motion is used by engineers in the design and fabrication of shotgun,pistol,revolvers,machine guns,bow and arow,and other lethal weapons.Design parameters are established via calculations with the three Newton’s law of motion.
