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Laws of Motion: Newton’s Second Law of Motion

Grade 3
Jul 28, 2023


We are surrounded by a huge number of objects. Some are moving, some are at rest, some are speeding up, and some are slowing down. In this session, we will be able to figure out the conditions under which an object speeds up or slows down by studying Newton’s second law of motion.


Newton’s First Law of Motion:

Sir Isaac Newton
Sir Isaac Newton

Newton’s first law states that,

“An object at rest remains at rest unless acted upon by an external force.

An object in uniform motion continues to move at the same pace and direction unless it is acted upon by an external force.”

Newton’s 1st law of motion
Newton’s 1st law of motion

The bowling pins stay at rest unless a bowling bowl hits them. Here the bowling bowl exerts an external force on the pins, which changes their state from rest to motion.

The bowling pins
The bowling pins

Newton’s Second Law of Motion:

Let us consider two objects, a heavy rock and a brick. When these two objects are pushed, it will be observed that it is easier to push a brick as compared to a heavy rock. This is because a rock is much more massive compared to a brick. Therefore, heavier objects require a greater force to be moved. Similarly, lighter objects require a smaller force to be moved.

Now, let us take two tennis balls and push ball 1 harder than ball 2. It will be found that ball 1 speeds up faster than ball 2. This means that a greater force makes a body speed up faster than a smaller force applied on it.

The pace of speeding up or slowing down of an object is called its acceleration. If a car is speeding up quickly, it is said to have greater acceleration.

Thus, ball 1 accelerates more than ball 2 as it is pushed harder.

Newton’s 2nd law states that “The force applied on an object is equal to the mass of the object times the acceleration that it attains.”



F = ma

Where m is the mass of the object, and a is the acceleration that it attains after force F is applied to it.

Newton’s 2nd law of motion - Example
Newton’s 2nd law of motion – Example

Questions and Answers:

  1. Arrange the objects in ascending order of the amount of force that they might require to be moved from their places
a. Elephant
a. Elephant
b. Cat
c. Dog


(b) < (c) < (a)


  1. The greater the force applied to an object, the greater its acceleration.
  2. The smaller the mass of an object, the smaller the force needed to move it.
newtons second law of motion


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