What is the projectile motion?
When any object is thrown into the air it is obvious that the object will drop on the ground. If you take an object to a certain height and drop it the object will drop straight vertically to the ground. However, if you throw that object with some velocity in the horizontal direction to the ground the result will be different. In this case, the object will not drop straight to the ground it covers a few horizontal directions as well. When the object is moving in a horizontal direction two types of forces are acting on it. The first force acting horizontally is given at the time when it was thrown and the second force acting from downward is gravity. The gravity acts on it in every position so the object will be in the air until the gravity overcomes the force that was given at the initial phase. After that, the object will be at rest on the ground. When an object is dropped vertically without giving any external force this object is said to be at free fall. In the free fall, the acceleration of that body is equal to g. Which is also known as acceleration due to gravity. An interesting fact is that if you throw any object horizontally it also accelerates with the same value as it is in free fall. This implies that the horizontal velocity is always constant in the whole period of projectile (in the time of flight), although the vertical velocity accelerates with the value g.
The illustration of projectile motion is given below.
Projectile fired at an angle with horizontal
Suppose an object is projected with initial velocity u and
at an angle θ
with ground. The velocity u has two components of velocities acting on it. The
velocity along x-axis will be u cosθ which remains constant in overall
time. But the velocity along y-axis u sinθ will affect by gravity.
The following diagram illustrates the path of a projectile and
motion of the object at every point of time of flight
 |
| The Trajectory of projectile with initial velocity u and at angle θ with ground Now,
let’s look at some application of projectile motion a) When stone thrown horizontallySuppose
that a stone is thrown from a certain height with initial velocity u the
horizontal component of velocity ux will remains same in whole
period of motion but the vertical velocity uy will be change with
time and its acceleration is equal to acceleration due to gravity. Let’s look
at the following diagram which shows the motion of stone thrown horizontally. |
b) A bomb dropped from an aeroplane
c) Principle of launching of satellite
Probably, one of the best example of projectile which is
used by mankind is launching of satellite. The principle of launching satellite
is based on the projectile motion. If an object is projected in such a way that
it won’t drop back to the ground it will be moving forever around the earth
with the velocity which is given at the initial phase. The following diagram is
shown below to illustrate the principle of launching of satellite.
Conclusion
The projectile motion is a motion of an object which is
thrown in the atmosphere that falls under the effect of only gravity. In
projectile motion, an object has two types of velocity. The first one is
velocity along the x-axis or horizontal velocity and another is the y-axis or
vertical velocity. The horizontal velocity remains constant all over the time
of motion and the vertical velocity is affected by gravity which means it
changes over time. There are many examples of projectile motion such as
throwing a stone horizontally, a bomb dropping from an airplane, the principle
of the launching of a satellite. The principle of the launching of the
satellite is one of the best example of projectile which is used by mankind.
With this technique, mankind launches many satellites in the sky which are used
for many fields such as radio, television, internet, astronomical research
etc.
