Physics 9th Class Chapter 2 Lecture 3 – Second Equation of Motions

Second Equation of Motion

Physics, the study of the fundamental principles that govern the behavior of matter and energy, is a captivating subject that allows us to decipher the mysteries of the physical world. In the ninth-grade curriculum, one of the most intriguing topics in physics is the second equation of motion. This equation unravels the intricacies of accelerated motion, shedding light on the relationships between displacement, initial velocity, acceleration, and time.

Unveiling the Equation

The second equation of motion is often represented as:

s=vt + 1/2at2


  • stands for displacement,
  • represents initial velocity,
  • denotes acceleration,
  • symbolizes time.

This equation serves as a powerful tool to analyze scenarios where an object experiences constant acceleration. Whether it’s a ball rolling down a ramp or a car accelerating on a straight road, this equation allows us to predict and understand their motion with precision.

Also Study: Chapter 2 Lecture 1

Study: Chapter 2 Lecture 1

Also Study: Chapter 2 Lecture 1

Breaking Down the Equation

  1. Displacement (): This refers to the change in the position of an object. It can be positive, negative, or zero, depending on the direction of motion. In the context of the equation, is the total distance traveled by the object.
  2. Initial Velocity (v): The initial speed of the object when the time measurement begins. This velocity might be in any direction and can be zero if the object starts from rest.
  3. Acceleration (): Acceleration is the rate at which an object’s velocity changes. It can be uniform or non-uniform, and it’s typically measured in meters per second squared (m/s2). If the object is slowing down, acceleration will be negative, and if it’s speeding up, acceleration will be positive.
  4. Time (): The duration for which the object experiences the given acceleration. It’s measured in seconds.

Real-World Applications

The second equation of motion finds its applications in various real-world scenarios. Let’s explore a few:

Projectile Motion

Consider a ball thrown into the air. Gravity acts as the acceleration, and this equation helps us determine how high the ball will go and how long it will take to return to the ground.

Automotive Industry

Car manufacturers and engineers utilize this equation to design vehicles that accelerate safely and efficiently. It helps them calculate the distance required for a car to come to a complete stop when brakes are applied.

Sports Analysis

In sports like athletics and motorsports, understanding the second equation of motion can help athletes and coaches optimize their training routines and race strategies. It can also provide insights into how fast an athlete can sprint or how quickly a race car can accelerate.

Solving Problems Using the Equation

To solve problems using the second equation of motion, follow these steps:

  1. Identify the values given in the problem for v, and t.
  2. Substitute these values into the equation.
  3. Calculate the result, which will be the displacement “.

Remember, consistent units are crucial for accurate calculations. Make sure all values are in the same units before plugging them into the equation.


The second equation of motion is a cornerstone of understanding accelerated motion in physics. By dissecting the relationships between displacement, initial velocity, acceleration, and time, this equation empowers us to analyze and predict the behavior of objects undergoing constant acceleration. From calculating the trajectory of a basketball to engineering safer cars, its applications extend across various fields. Embracing this equation illuminates the path toward unraveling the mysteries of motion and harnessing its principles for the betterment of our world.

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