YASHPAL KASHYAP

GRAVITY : WHY ALL BODIES FALL AT SAME RATE

 

Illustration of Sir Isaac Newton holding apple in hand and looking up at tree

 

One of the four fundamental forces of  nature is " Gravity ". Though, every object in the universe has his specific value of weight & mass. Even though it is the matter of fact that “Every Body On Our Earth Falls At Same Rate”. Thats pretty amazing, Isn't it ? This was first given by sir Issac Newton”. Sir Issac Newton, Great Man With “Extraordinary Thinking” Capabilities.

 

Why All Bodies Fall At Same Rate :

 

So in this post I will be discussing about how the Gravity makes all the object, with various kind of weight and mass, fall towards earth at the same rate. This amazing fact ( Why All Bodies Fall At Same Rate ) can be explained by “Newton Second Law Of Motion” & “Newton Law Of Gravity”. Many of you guys reading this post might already have come across Newton Laws Of Motion. Hence we will be learning something about Newton Second Law Of Motion .

 

 

Newton Second Law Of Motion :

 

 

  Newton Second Law Of Motion states that :

 

“The rate of change of speed ( Acceleration ) of an object will be directly proportional to the force and inversely proportional to the mass of the object”.

In other words we can say that the rate of change of speed of an object will be directly proportional to the force applied on it . That is, Force is directional proportional to Acceleration. In addition the Force will be directly proportional to the Mass. The the equation we get from above are as follows :

 

 

The above equation also shows that the Acceleration will be inversely proportional to the Mass of the object , Which means that as Mass increases the acceleration will decrease at a constant Force.

 

Example :

Let say that a Car of Mass M , Have a Acceleration A , At a constant Force F. Suppose the car is moving with a certain Speed S. In this sceneario if we increase the Weight of the car and the Engine is providing the constant Force F, As a result the Speed of the car will be slowed down. This shows that the Acceleration is directional proportional to the Force & inversely proportional to the Mass of the moving object.

 

 

 

Newton Law Of Gravity :

 

 

According to Newton law of Gravity :

" Every body attracts every other body in the universe. The force of attraction between two bodies will be directly proportional to the product of the Masses and inversely proportional to the square of the Distance between them. "

 

 

Example :

Let us consider a body of Mass M1 Which attracts another body of Mass M2 with a Force F. Now the first body has it's Mass Doubled , Then the Force Of Attraction between the two bodies will also be Doubled. Suppose the Mass of the First Body is Doubled & the Mass of the Second Body is Increased by Three Times, Then the Force Of Attraction between the two bodies will increase by Six Times ( 2 × 3 = 6 ).

 

 

 

 

We can think that the first body with it's Mass doubled has been formed with a new body of same Mass. In other words the Force is Directly Proportional to it's Mass.

 

F ∝ M

 

 

Comparison Between The Above Two Laws :

 

SECOND LAW OF MOTION

At Constant Force

Mass Increases 

Acceleration Decreases

 

LAW OF GRAVITY

Mass Increases

Force Of Attraction Increases

 

F ∝ M × A                       F ∝ M

F = K M × A                     F = KA

 

Where, K is constant

These two laws will Exactly Cancel Out each other and giving out the final equation as,

F = M

Thus, The body of Mass M falling towards Earth will have the Gravitational Force Of Attraction . Now if the Mass of the object is Doubled then the Gravitational Force Of Attraction will also be Doubled, But if the Mass of object is Doubled, Then Acceleration of that object will Decrease. Thus, The Rate Of Fall Of The Object Will Be Same .

Always Remember : 

The feather and metal ball will also fall at same rate, But the feather will be slowed down because of its air resistance quality. Thus, As Compared To Metal Ball , Feather comes slowly down to earth .