#physics #momentum #basics #textbook
Pg:- 54,55
Ch:- 3
Momentum is a fundamental concept in physics that describes the quantity of motion an object possesses. It is closely tied to both the object's mass and its velocity. In simple terms, momentum reflects how difficult it is to stop a moving object. The greater the momentum, the harder it is to stop.
1. Definition and Formula
Momentum (p) is defined mathematically as the product of an object's mass (m) and its velocity (v):
p=m⋅v
Where:
p is the momentum vector,
m is the mass of the object (a scalar quantity),
v is the velocity vector.
Momentum is a vector quantity, meaning it has both magnitude (how much momentum) and direction (the direction of motion).
2. Units of Momentum
The SI unit of momentum is kilogram meters per second (kg·m/s). This comes directly from multiplying the units of mass (kilograms) and velocity (meters per second).
3. Conservation of Momentum
One of the most important principles associated with momentum is the law of conservation of momentum. This law states that in a closed system, where no external forces are acting, the total momentum remains constant.
This means that if two or more objects interact (for example, through a collision), the total momentum of all the objects before the interaction will equal the total momentum after the interaction, provided no external forces interfere.
4. Types of Momentum
Linear Momentum: This is the standard momentum described above, where the object moves in a straight line.
Angular Momentum: When an object rotates or revolves around a point (like a planet orbiting a star or a spinning top), it has angular momentum. Angular momentum depends on the object's moment of inertia and angular velocity, and is given by the formula:
L=r×p
where:
L is the angular momentum,
r is the position vector relative to the axis of rotation,
p is the linear momentum,
and × represents the cross-product between the two vectors.
Like linear momentum, angular momentum is also conserved in an isolated system.
5. Collisions and Momentum
Momentum plays a key role in understanding collisions:
Elastic collisions: In these, both momentum and kinetic energy are conserved.
Inelastic collisions: Momentum is conserved, but kinetic energy is not fully conserved (some is converted into heat, sound, or deformation).