Kinematics Formulas
Introduction:
Kinematics formulas are mathematical equations used to describe the motion and position of objects in physics. These formulas provide insights into the relationship between an object’s displacement, velocity, and acceleration. They allow us to calculate and understand various aspects of motion, such as speed, time, and trajectories. By utilizing these formulas, we can analyze and quantify the geometric and dynamic properties of objects in motion, contributing to a deeper understanding of the principles governing the physical world.
Kinematical Equations:
The kinematic equations describe the motion of objects in terms of displacement, velocity, acceleration, and time. They are derived from basic principles of calculus and are applicable to objects undergoing constant or uniformly accelerated motion.
There are three fundamental kinematic equations that are given by:
Here, ‘u’ is the initial velocity, ‘v’ is the final velocity, ‘a’ is the acceleration, ‘t’ is the time,
and ’s’ is the distance or displacement of the body.
The kinematic equations are primarily used for linear or straight-line motion. They assume constant acceleration, uniform motion, and no external forces acting on the object.
Application of Kinematics Formulas:
Kinematics formulas have wide-ranging applications in various fields. In physics, they are essential for analyzing and predicting the motion of objects, whether it be the trajectory of a projectile, the motion of planets, or the behavior of particles in particle accelerators. They are also used extensively in engineering and robotics to design and control the motion of mechanical systems and robots. In sports, kinematics formulas are used to analyze athletes’ movements, measure performance metrics such as speed and acceleration, and optimize techniques. Additionally, these formulas find applications in computer graphics, animation, and virtual reality to simulate realistic motion and create lifelike virtual environments.
Solved Examples on Kinematics Formulas:
Example 1: A car accelerates uniformly from rest at a rate of 3 m/s². How far does it travel in 5 seconds?
Solution:
Given:
Initial velocity (u) = 0 m/s
Acceleration (a) = 3 m/s²
Time (t) = 5 s
We need to find the displacement (s).
Using Equation 2: s = ut + (1/2)at²
s = (0)(5) + (1/2)(3)(5²)
s = 0 + (1/2)(3)(25)
s = 0 + 37.5
s = 37.5 m
Therefore, the car travels a distance of 37.5 meters in 5 seconds.
Example 2: A ball is thrown vertically upwards with an initial velocity of 20 m/s. How high does it go before coming back down?
Solution:
Given:
Initial velocity (u) = 20 m/s
Acceleration due to gravity (g) = -9.8 m/s² (negative since it acts downwards)
We need to find the maximum height reached, which is the displacement at the highest point (where the velocity becomes zero).
Using Equation 3: v² = u² + 2as
At the highest point, the final velocity (v) is 0 m/s.
0² = (20)² + 2(-9.8)s
0 = 400 – 19.6s
19.6s = 400
s = 400 / 19.6
s≈ 20.41 m
Therefore, the ball reaches a maximum height of approximately 20.41 meters.
Example 3: A cyclist starts from rest and accelerates uniformly at 2 m/s² for 10 seconds. Then, the cyclist maintains a constant velocity for the next 20 seconds. Finally, the cyclist decelerates uniformly at 3 m/s² until coming to rest. Calculate the total displacement of the cyclist.
Solution:
Phase 1: Acceleration
Initial velocity (u) = 0 m/s
Acceleration (a) = 2 m/s²
Time (t) = 10 s
Using Equation 2: s = ut + (1/2)at²
s1 = (0)(10) + (1/2)(2)(10²)
s1 = 0 + 100
s1 = 100 m
Phase 2: Constant Velocity
Velocity (v) = 20 m/s (since the cyclist maintains constant velocity)
Time (t) = 20 s
Using Equation 4: s = v x t
s2 = 20 m/s x 20
s2 = 400 m
Phase 3: Deceleration
Final velocity (v) = 0 m/s
Acceleration (a) = -3 m/s² (negative sign indicates deceleration)
Time (t) = ?
Using Equation 1: v = u + at
0 = 20 + (-3)t
3t = 20
t = 20/3 ≈ 6.67 s
Using Equation 2: s = ut + (1/2)at²
s3 = (20)(6.67) + (1/2)(-3)(6.67)²
s3 = 133.4 – 66.7
s3 = 66.7 m
Total displacement = s1 + s2 + s3
Total displacement = 100 + 400 + 66.7
Total displacement = 566.7 m
Therefore, the total displacement of the cyclist is 566.7 meters.
Frequently Asked Questions on Kinematics Formulas:
1: What are the main 3 kinematical equations?
Answer: The main formulas of kinematics involve the relationships between displacement (s), velocity (v), acceleration (a), and time (t). Here are 3 main formulas:
v = u + at
(Final velocity equals initial velocity plus acceleration multiplied by time.)
s = ut + (1/2)at²
(Displacement equals initial velocity multiplied by time plus one-half acceleration multiplied by the square of time.)
v² = u² + 2as
(Final velocity squared equals initial velocity squared plus twice acceleration multiplied by displacement.)
2: What is kinematics first equation?
Answer: First equation of kinematics is v= u + at where 𝑢 is its initial velocity and 𝑎 is its acceleration.
3: Who is the father of kinematics?
Answer: The father of kinematics is often considered to be Sir Isaac Newton. Newton’s laws of motion and his contributions to the field of mechanics laid the foundation for the study of kinematics. His work, especially in his book “Mathematical Principles of Natural Philosophy” (also known as “Principia”), introduced the concepts of motion, forces, and the mathematical equations that govern them. Newton’s contributions revolutionized the understanding of motion and established the fundamental principles of kinematics that are still widely used today.
4: Why is it called kinematics?
Answer: Kinematics is the branch of physics that deals with the study of motion, specifically focusing on the description and analysis of the motion of objects without considering the causes of the motion. It is concerned with concepts such as position, velocity, acceleration, and time. The term “kinematics” is derived from the Greek words “kinēsis” meaning motion and “kinein” meaning to move. It is called kinematics to distinguish it from dynamics, which involves studying the forces and causes that produce motion.
5: What are the units of kinematics?
Answer: Kinematics involves various quantities related to motion, each with its own specific units. The units commonly associated with kinematics include:
- Position: The unit of position is typically measured in meters (m), representing the distance from a reference point.
- Velocity: Velocity is the rate of change of position and is measured in meters per second (m/s).
- Acceleration: Acceleration represents the rate of change of velocity and is measured in meters per second squared (m/s²).
- Time: Time is a fundamental quantity in kinematics and is measured in seconds (s).
These units are used to quantify and describe the motion of objects in kinematics.
6: What is the use of kinematics?
Answer: Kinematics is used to study and analyze the motion of objects without considering the forces involved. It helps in understanding the concepts of position, velocity, acceleration, and time in relation to the motion of objects. Kinematics is widely applied in fields such as physics, engineering, robotics, and animation to predict and describe the movement of objects, design mechanical systems, simulate motion, and optimize performance. It forms the foundation for understanding and analyzing various types of motion, providing valuable insights into the behavior of objects in motion.
7: What does v stand for in motion?
Answer: In the context of motion, “v” typically represents the symbol for velocity. It is measured in units of distance per unit time, such as meters per second (m/s) or kilometers per hour (km/h). The direction of velocity is typically indicated using a positive or negative sign, or by specifying a specific angle or direction.
8: Why distance is denoted by s?
Answer: The origin of the symbols for displacement (∆s) and distance (∆s) is spatium, the Latin word for space (like the space between two locations).
9: What are the 4 variables in kinematics?
Answer:
Displacement (s): Displacement refers to the change in position or the distance between the initial and final positions of an object. It is a vector quantity that includes both magnitude and direction.
Velocity (v): Velocity represents the rate at which an object changes its position. It is the derivative of displacement with respect to time and is also a vector quantity, combining both speed and direction.
Acceleration (a): Acceleration is the rate at which an object’s velocity changes. It is the derivative of velocity with respect to time. Acceleration can be either positive (speeding up) or negative (slowing down), and it is also a vector quantity.
Time (t): Time is a scalar quantity that measures the duration or interval during which the motion takes place. It is typically measured in seconds (s) or any other appropriate unit of time.
These four variables—displacement, velocity, acceleration, and time—form the foundation of kinematics and are used to describe the motion of objects, calculate their changes over time, and solve various problems related to motion and dynamics.
10: What is free fall formula?
Answer: The formula for free fall describes the motion of an object falling freely under the influence of gravity, assuming no air resistance. In free fall, the only force acting on the object is the force of gravity. The formula for free fall involves the variables of time (t) and acceleration due to gravity (g).
The general formula for free fall is:
h = (1/2)gt²
Where:
h is the height or vertical displacement of the object,
g is the acceleration due to gravity (approximately 9.8 m/s² on Earth),
t is the time elapsed.
It is derived from the second kinematical equation: s = ut + (1/2)at²
