How does a Parachute Work?

            A parachute is an umbrella like device used for slowing the descent of a body falling through the atmosphere. Originally, it was conceived as a safety measure for a fighter pilot in a flying aircraft. Now parachutes have wide application in times of war and peace; for example, they are used for safe dropping of supplies of essential items in times of emergency as well as for landing of personnel.

Parachute

            The first man to demonstrate the use of parachute was Louis Sebastian Linesman of Franc in 1783. André Jacques granaries was first to use a parachute on regular basis demonstrating a number of exhibition jumps including one from a height of about 2400 meters in England in 1801.

            Early parachutes were made of canvas and later silk was used. Captain Albert berry of the U.S. army made the first successful descent from an aero plane in 1912. in world war II, parachutes were used for a variety of purposes i.e. landing of special troops for comber infiltrating agents into enemy territories and dropping of weapons, etc. parachutes are made of nylon and are generally about 7 to 9 meters wide, when open. Parachutes used for dropping heavy cargo may be as wide as 30 meters when open.

            Now the question arises how doe s a parachute works?

            A parachute operates on the simple principles involving the force of gravity and air resistance which are the two forces that act upon any falling object. A parachute starts falling towards the ground due to the force of gravity but due to resistance of air caught in the open parachute the speed of the fall slowed down.

            During the descent of a parachute at a certain point when the air resistance and the pull of gravity are evenly balanced the parachute reaches a speed called terminal velocity. At this stage parachute descends at a constant speed.

How Fast do the Objects Fall?

            When we know a ball up in the air, we observe that it gradually slows down, and the almost comes to a stand still, before it stars falling back to the ground. While it starts falling back to the ground. While falling down, it should be noted that the initial speed is low but gradually becomes high.

            The earth attracts all objects towards its centre with a force known as the force of gravity. The ball falls to the ground due to this force gravity. The force of gravity makes all falling objects acquire an acceleration, which is called the acceleration due to gravity. It is denoted by ‘g’.

            The acceleration due to gravity accelerates the ball roughly at 9.8 meters per second per second 32 feet per second. This means that each second the object would move 9.8 meters faster than the previous second. The speed of the ball at different intervals of time varies as follows.

            To begin with, the ball or a falling object is stationary or its speed is zero. At the end of 1 second, it travels 9.8 meters per second. At the end of 2 seconds, it moves 19.6 meters per second and at the end of 3 seconds, 29.4 meters per second and so on. In fact, every second, the object falls 9.8 meters per second faster than its speed in the previous second.

            Acceleration due to gravity is defined as the rate of change in velocity of a falling object with respect to time due to the force of gravity. Because it is measure of rate of change of velocity, it is expressed in meters per second, and is termed as meters per Second Square.

            The acceleration of body or object falling freely in vacuum varies slightly form place to place due to slight variation in the gravitational force of the earth, as the distance of the place form the center of the earth varies. In London, the value of ‘g’ is 9.807 meters per second per second, as North Pole 9.8 meters per second per second, and at the equator it is 9.79 meter per second. At sea level in Washington, it is 9.8008 meters per second per second.

            One of the important points to note about falling objects is that however heavy they might be, they all fall at the same rate. But, air resistance may retard the speed of falling objects. The famous scientist Galileo demonstrated this fact by dropping a heavy cannon ball and a light musket ball at the same time form the leaning tower of Pisa. Both the objects hit at the ground at the same time.

            Air resistance is the main reason why some objects fall slower than others. A feather, for example, floats slowly downwards because it faces more air resistance due to its relatively large surface area. A smooth, pointed bullet will fall faster than a feather because it experiences less air resistance. In vacuum both objects will fall at the same speed, as there would not be any air resistance.