Do bodies with different masses when dropped from a height in free space, reach the earth at different times depending on their weight? Well, do heavier bodies actually fall faster? Let us explore what Physics has to say in this.
In fact this is what was considered as an official honest-to-goodness law of Physics, stated by Aristotle in ancient Greece. Beyond this codification, there was no discovery until, an Italian physicist in the Renaissance era, Galileo Galilei, proved it wrong. The discovery of most counter-intuitive property of Physics came as a surprise to many at that time.
Galileo performed an experiment from the top of the leaning tower of Pisa, in Italy. He dropped two spheres of different weights and observed that both the spheres hit the ground at the same time.
Hence, the misconception has been debunked. Everything on planet Earth will fall at the same speed, if dropped from the same height.
So why was the earlier misconception there? If you drop a hammer and a feather from a height, it is obvious that the hammer would hit the ground earlier. But what people did not consider was an invisible property in the atmosphere, called air resistance. Objects that are light such as feathers, pieces of paper etc. stay longer in air not because of their weight but because of the resistance that air offers when on their downwards motion. You will see that a flat paper when crumpled into a ball falls faster than when it is not crumpled. Therefore, mass is not the favorable factor for the object to hit the ground first.
Things are a little different in vacuum though. Since there is no air resistance in vacuum, you can see the same two objects take the same time to reach the ground.
However, let’s see how we can use our knowledge of Physics to explain this fact further.
According to Newton’s Second Law of Motion, the force with which the body falls (or weight)
(Where, ‘m’ is the mass of a body and ‘g’ the acceleration due to gravity)
Now, using the formula for the gravitational force on the body, we have
So, the above two equations imply that,
From this equation, we can see that since the value of G is constant and so is mass and radius of the earth, the acceleration due to gravity is same for all practical purposes.
This is why, everything on earth, no matter how light or heavy, falls to the ground at the same speed when dropped from the same height. This type of motion is typically referred to as Free Fall. The sole force acting upon the object is gravity, in this type of motion. In a free fall, the object falls at a rate of 9.8 m/s2 near the surface of the earth.
Try this out at home. Take a golf ball and a bowling ball and drop them from the side of a building simultaneously. However, before you try this, make sure you have an observer standing on the ground first to ensure that no one passes by when you are experimenting.
Which ball hit the ground first? Are you surprised by the result?
Princy P. John is a qualified Physicist, armed with a Bachelor of Science (Physics Hons.) from St. Stephens, Delhi University and a Masters in Physics. She is an integral part of the Science channel at Zigya and oversees Physics content for all classes. She taps onto the pulse of events happening globally on scientific platforms and brings value to Zigya with her knowledge, wit and resolve. Princy also provides key management updates of the editorial board and aids in the decision making process at Zigya.
Follow her work at www.zigya.com