**Free Fall vs Projectile Motion**

Free fall and projectile motion are two very important concepts discussed under mechanics. These two phenomena are of utmost importance and play a vital part in fields such as space exploration, weather systems, aviation, military applications and even sports. It is vital to have a clear understanding in these concepts in order to excel in such fields. In this article, we are going to discuss what free fall and projectile motion are, their applications, similarities between these two, definitions of free fall and projectile motion and finally the difference between free fall and projectile motion.

**What is Free Fall?**

自由落体,描述物体的运动here the gravitational force is the only force acting on the object. The motion of the object is an inertial motion. To understand the concept of free fall properly, one must first understand the gravitational field and gravitational potential. Gravity is the force that occurs due to any mass. Mass is the necessary and the sufficient condition for gravity. There is a gravitational field defined around any mass. Take masses m_{1}and m2placed in a distance r from one another. The gravitational force between these two masses is G.m_{1}.m_{2}/ r^{2}where G is the universal gravitational constant. The gravitational potential at a point is defined as the amount of work done on a unit mass when bringing it from infinity to the given point. Since the gravitational potential at infinity is zero, and the amount of work has to be done is negative, the gravitational potential is always negative. The gravitational potential energy of an object is defined as the work done on the object when the object is taken from infinity to the said point. When an object is on a free fall, the gravitational potential energy of the object is converted to kinetic energy. This causes the velocity of the object to be increased thus creating acceleration. This acceleration is known as the gravitational acceleration. Objects orbiting around planetary bodies are on a constant, free fall state. The thrusters on such satellites are used to increase the potential energy of the satellite so that it would not crash into the planet.

**What is Projectile Motion?**

The motion of an object, which is projected or thrown, is known as the projectile motion. The projectile motion can take place in any situation. Under a gravitational field when the air resistance is not present, projectile motion can be considered as a free fall. Projectiles play a very important role in fields such as military technology, space exploration and even sports. The initial velocity given to the object by throwing is stored in the system as kinetic energy. The maximum height of the projectile depends on the angle the object was thrown, the initial velocity and the air resistance. Most of the times the air resistance is neglected to make the calculation easy.

• Free fall can only occur under gravity, but projectile motion can occur under any force field. • Free fall is a special case of projectile motion where the initial velocity is zero. • Free fall cannot occur in situations where the air resistance is present; the object will come to a terminal velocity, but projectile motion can occur in such situations. |

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