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Linear Momentum Formula Explained with Solved Examples

The concept of kinetic energy is related to the conservation of mechanical energy, which states that the total mechanical energy (the sum of kinetic and potential energy) of an isolated system remains constant unless acted upon by external forces.
authorImageMurtaza Mushtaq11 Sept, 2023
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Linear Momentum Formula

Linear Momentum Formula is the energy an object possesses due to its motion. It's one of the fundamental concepts in physics and is defined as the energy that an object has because of its velocity (speed) and mass. In other words, when an object is in motion, it has kinetic energy associated with that motion.

The formula for kinetic energy is: Where: - KE represents the kinetic energy in joules (J). - m is the mass of the object in kilograms (kg). - v is the velocity (speed) of the object in meters per second (m/s).

Key points about kinetic energy:

  1. Depends on Mass and Velocity: Kinetic energy is directly proportional to both the mass and the square of the velocity of the object. This means that increasing either the mass or the velocity will increase the kinetic energy.
  2. Scalar Quantity: Kinetic energy is a scalar quantity, meaning it only has magnitude (a numerical value) and no direction. It's always positive or zero and does not have a directional component.
  3. Conservation of Energy: According to the law of conservation of energy, the total mechanical energy (which includes both kinetic and potential energy) of an isolated system remains constant if there are no external forces acting on it. This principle is often used in various physical problems.
  4. Units: The SI unit of kinetic energy is the joule (J), which is equivalent to one kilogram-meter squared per second squared (1 kg·m^2/s^2).

Also Check - Kinetic Energy Formula

In practical terms, kinetic energy helps describe how fast an object is moving and how much "energy of motion" it possesses. For example, a speeding car has a significant amount of kinetic energy, and a slowly moving object has less kinetic energy. Understanding kinetic energy is essential in many areas of physics and engineering, particularly in the analysis of motion and collisions. Kinetic energy is a fundamental concept in physics that represents the energy an object possesses due to its motion. It's a measure of how much work an object could do because of its motion. In other words, it quantifies the energy associated with the movement of an object. Kinetic energy depends on two factors: - Mass (m): The mass of the object in kilograms (kg). This represents how much matter is in motion.

Also Check - Unit, Dimension & Vector Formula

- Velocity (v): The velocity of the object in meters per second (m/s). This represents how fast the objectis moving.

Linear Momentum (p):

Linear momentum, often denoted as "p," is another fundamental concept in physics that describes the quantity of motion of an object. It is a vector quantity, meaning it has both magnitude and direction. Linear momentum depends on two factors: - Mass (m): Just like in kinetic energy, it represents the mass of the object in kilograms (kg).

Also Check - Work, Energy & Power Formula

- Velocity (v): This represents the velocity of the object in meters per second (m/s). However, unlike kinetic energy, linear momentum doesn't involve squaring the velocity. The formula for linear momentum is: p = m * v Linear momentum is directly proportional to both the mass and the velocity of the object. Now, let's define the relationship between kinetic energy and linear momentum: The relationship between kinetic energy (KE) and linear momentum (p) can be expressed as follows: KE = (1/2) * (p 2 / m) This equation shows that kinetic energy is directly related to the square of the magnitude of linear momentum (p) and inversely related to the mass (m) of the object. In essence, it tells us that as an object's linear momentum increases (either by increasing its velocity or mass), its kinetic energy also increases, but the relationship is quadratic, meaning that a small increase in momentum can result in a much larger increase in kinetic energy.

Some Examples

Let's go through a couple of examples to illustrate the relationship between kinetic energy (KE), linear momentum (p), and how changes in mass or velocity affect them. Example 1: Car Moving on the Highway Imagine a car traveling on a highway with a mass of 1,000 kilograms (m) and a velocity of 30 meters per second (m/s).
  1. Calculate the linear momentum (p):
p = m * v = 1,000 kg * 30 m/s = 30,000 kg m/s
  1. Calculate the kinetic energy (KE):
KE = (1/2) * m * v^2 = (1/2) * 1,000 kg * (30 m/s)^2 = 450,000 J (joules) Now, let's see how changes in velocity affect kinetic energy and momentum: Example 2: Doubling the Velocity Let's say the car's velocity is doubled to 60 m/s while keeping the mass constant at 1,000 kg.
  1. Calculate the new linear momentum (p):
p = m * v = 1,000 kg * 60 m/s = 60,000 kg m/s
  1. Calculate the new kinetic energy (KE)
KE = (1/2) * m * v^2 = (1/2) * 1,000 kg * (60 m/s)^2 = 1,800,000 J By doubling the velocity while keeping the mass constant, the linear momentum doubled from 30,000 kg m/s to 60,000 kg m/s, but the kinetic energy increased fourfold from 450,000 J to 1,800,000 J. This demonstrates how kinetic energy is proportional to the square of velocity. Example 3: Doubling the Mass Now, let's keep the velocity at 30 m/s but double the mass of the car to 2,000 kg.
  1. Calculate the new linear momentum (p):
p = m * v = 2,000 kg * 30 m/s = 60,000 kg m/s
  1. Calculate the new kinetic energy (KE):
KE = (1/2) * m * v^2 = (1/2) * 2,000 kg * (30 m/s)^2 = 900,000 J By doubling the mass while keeping the velocity constant, the linear momentum doubled from 30,000 kg m/s to 60,000 kg m/s, but the kinetic energy only doubled from 450,000 J to 900,000 J. This shows that kinetic energy is directly proportional to mass but not linearly; it increases linearly with mass. These examples illustrate the relationship between kinetic energy and linear momentum and how changes in mass and velocity affect them. Kinetic energy is affected by both mass and the square of velocity, while linear momentum depends linearly on both mass and velocity.

Linear Momentum Formula FAQs

What is kinetic energy, and how is it different from linear momentum?

Kinetic Energy (KE): Kinetic energy is the energy an object possesses due to its motion. It depends on both the mass and the square of the velocity of the object. KE is a scalar quantity and is measured in joules (J).

How are kinetic energy and linear momentum related mathematically?

 The mathematical relationship between kinetic energy (KE) and linear momentum (p) is given by the formula: KE = (1/2) * (p^2 / m). This equation shows that kinetic energy is proportional to the square of the magnitude of linear momentum and inversely proportional to the mass of the object.

What happens to kinetic energy when an object's velocity doubles?

  When an object's velocity doubles, its kinetic energy increases by a factor of four. This is because kinetic energy is directly proportional to the square of velocity. So, if the velocity is doubled, the kinetic energy will be four times greater.

What physical principles are associated with kinetic energy and linear momentum?

Conservation of Energy: The concept of kinetic energy is related to the conservation of mechanical energy, which states that the total mechanical energy (the sum of kinetic and potential energy) of an isolated system remains constant unless acted upon by external forces.    - Conservation of Linear Momentum: Linear momentum is associated with the conservation of linear momentum principle, which states that in the absence of external forces, the total linear momentum of an isolated system remains constant. This principle is often applied in the analysis of collisions and interactions between objects.
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