Table of Contents
1.Projectile Motion
*Definition
*Discovery and Evolution
~Aristotle’s Theory of Motion
~ Medieval Scientists
~ The Renaissance
~ Galileo’s Work
*Applications
2. Trebuchet
* Definition
* History
* Structure
* Principle
* Working
PROJECTILE MOTION
Definition
Projectile Motion is a form of motion experienced by an
object or particle that is thrown near the Earth’s surface and
moves along a curved path under the action of gravity only.
Discovery And Evolution
Aristotle’s Theory of Motion
The Greek thinker stated that if a body is moving, something
external is required to keep it moving.
E.g.: - An Arrow shot from a bow keeps flying since the air
behind the arrow keeps pushing it.
Medieval Scientists
Aristotle’s Medieval successors internalized this force
in the projectile itself called it “impetus.” This impetus
caused the object to move in a straight line until it was
expanded, at which point the object fell straight to the
ground. While objects projected, through small
distances may appear to behave in this manner, under
closer inspection and when viewing projectiles
traveling greater distances, it becomes clear that
projectiles do not behave in this manner. Representing
the focus especially in the arts was on representing as
accuratelywhen viewing
The Renaissance
During The Renaissance, the focus, especially in the
arts, was on representing as accurately as possible the
real world whether on a 2-dimensional surface or a
solid such as marble or granite. This required two
things. The first was new methods for drawing or
painting, e.g., perspective. The second, relevant to this
topic, was careful observation.
With the spread of cannon in warfare, the study of
projectile motion had taken on greater importance,
and now, with more careful observation and more
accurate representation, came the realization that
projectiles did not move the way Aristotle and his
followers had said they did: the path of a projectile did
not consist of two consecutive straight-line
components but was instead a smooth curve.The story
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and now with more
(The
Renaissance)
Galileo’s Work
Now someone needed to come up with a method to
determine if there was a special curve a projectile
followed. But measuring the path of a projectile
was not easy.
Using an inclined plane, Galileo had performed
experiments on uniformly accelerated motion, and
he now used the same apparatus to study projectile
motion. He placed an inclined plane on a table and
provided it with a curved piece at the bottom which
deflated an inked bronze ball into a horizontal
direction. The ball thus accelerated rolled over the
table top with uniform motion and then fell off the
edge of the table where it hit the floor, it left a
small mark. The mark allowed the horizontal
velocity and vertical drop. Galileo was able to
determine that the path of a projectile is parabolic.
Inclined plane on a table and provided
(e.g. 1)
(e.g. 2)
Applications
1. Ballistics is the science of mechanics that
deals with the flight, behavior, and effects of
projectiles, especially bullets, unguided bombs,
rockets, or the like; the science or art of designing
and accelerating projectiles so as to achieve a
desired performance.
2. A ballistic missile is a missile only guided
during the relatively brief initial powered phase of
flight, and whose subsequent course is governed
by the laws of classical mechanics (which includes
projectile motion). It plays an important role in
sports. It is the art of designing and accelerating
projectiles so as to achieve a desired performance.
E.g.: - Football, basketball and rugby. The tale of
chocolate cultivation now circles the world. The
earliest usage of chocolates dates back before
olmec. The oldest known cultivation and usage of
cocoa was in Puerto Escondio Hondurasas
projectiles so as to achieve a desired performance
like slingshots catapults and trebuchets based on
a desired performance
3. In materials handling industries, often times,
a designer will use projectile motion to determine
the anticipated trajectory of the discharge form
bulk solids belt conveyors and bucket elevators.
They use the predicted trajectories to aid in
designing material collection chutes, etc.
4. Many weapons are based on projectile
motion, like catapults, slingshots and trebuchets.
TREBUCHET
Definition
A trebuchet is a type of catapult, a common type
of siege engine which uses a swinging arm to
throw a projectile.
The first recorded use of traction trebuchets was it
ancient china. They were probably used by the mohists
as early
History
1. The first recorded use of traction trebuchets
was in ancient China. They were probably used
by the Mohists as early as 4th century BC.
2. The hand trebuchet was a staff sling mounted
on a pole using a lever mechanism to propel
projectiles. Basically, a one-man traction
trebuchet, it was used by emperor Nicephorus II
Phokas around 965 to disrupt enemy formations
in an open field.
3. The earliest known description and illustration
of a counterweight trebuchet comes from a
commentary on the conquests of Saladin by
Maedi ibn Ali al-Tarus in 1187.
4. The Couillard is a smaller version of a
counterweight trebuchet with a single frame
instead of the usual double “A” frames. The
counterweight is split into two halves to avoid
hitting the center frame.
5. With the introduction of gunpowder, the
trebuchet began to lose its place as the siege
engine choice of cannon.
Structure
In general, the trebuchet consists of a long beam that
pivots around an axle positioned above ground on a
wooden structure. The axle divides the beam into a
long short arm. The projectile is placed at the terminal
end of the long arm and pulling ropes or a
counterweight is positioned at the terminal end of the
short arm. Historically, there were three basic forms of
trebuchets: traction machines, powered by crews
pulling on ropes; counterweights machines, activated
by the fall of large masses; and hybrid machines
employing both pulling ropes and falling in large
masses. Counterweight trebuchets were the most
powerful of the three types. Large counterweight
trebuchets could throw 300 kg rocks over 200 yards.
The most massive trebuchets were reported to throw
in excess of 1000 kg.
Principle
The trebuchet relies on the principle that stored
potential energy of the counterweight can be
converted into kinetic energy of the payload, launching
it into the air. It is also based on the principle of
projectile motion.
Working
A trebuchet works by using the energy of a falling (and
unhinged) counterweight to launch a projectile (the
payload), using mechanical advantage to achieve a
high launch speed. For maximum launch speed the
counterweight must be much heavier than the payload,
since this means that it will fall quickly.
The counterweight pivots around a much shorter
distance than the payload end. The advantage of this is
that the payload end of the beam reaches a much
higher linear velocity than the counterweight end of
the beam. This is the principle of mechanical
advantage, and is what allows payload to reach a high
launch velocity. However, because the counterweight
pivots around a much shorter distance, its weight must
be much greater than the weight of the payload, to get
a high launch velocity.
BIBLIOGRAPHY
BOOKS:
Physics(part-1)- textbook for class 11(NCERT)
Galileo’s notes on Motion By Stillman Drake
The Art of Renaissance Science Galileo and
Perspective featuring Joseph W. Duben
Galileo Gleanings XXII: Galileo’s Expeimental
Confirmation of Horizontal Inertia: Unpublished
Manuscripts by S. Drake.
WEBSITES:
Wikipedia.org
Galileo.edu
Scienceexplained.com
Quora.com
Sciencebuddies.com
Real-world-physiscs-problems.com
