XI Physics Chapter 7 Vocabulary: Momentum, Impulse, Centre of Mass, and Collisions

Vocabulary flashcards covering linear momentum, impulse, conservation laws, center of mass definitions, variable mass motion, and system dynamics based on Class XI Physics Chapter-7.

Linear Momentum of a Particle

The product of a particle's mass $m$ and its velocity $v$, defined by the formula $p = m v$.

Linear Momentum of a System

The vector sum of the linear momenta of all individual bodies in a system, expressed as $P = \sum m_i v_i$.

Impulse of a Force

The integral of a force $F$ over a time interval from $t_1$ to $t_2$, defined as $J = \int_{t_1}^{t_2} F \, dt$, which simplifies to $J = F \Delta t$ when the force is constant.

Impulse Momentum Theorem

The principle stating that the vector sum of all external impulses acting on a mechanical system equals the change in the linear momentum of the system, expressed as $J_{ext} = \Delta P_{sys}$.

Law of Conservation of Linear Momentum

The law stating that if no net external impulse acts on a mechanical system during a period of time, the total linear momentum of the system remains conserved.

Center of Mass (Velocity Definition)

An imaginary point whose velocity $V_{cm}$ satisfies the system momentum relation $P = \sum m_i v_i = M V_{cm}$, where $M$ is the total mass of the system.

Center of Mass (Acceleration Definition)

An imaginary point whose acceleration $a_{cm, earth}$ satisfies Newton's Second Law for a mechanical system: \sum F_{ext} = \sum m_i a_{i, earth} = M a_{cm, earth}.

Position Vector of CM (Discrete Masses)

The position vector of the center of mass for a collection of point masses or rigid bodies, given by $r_{CM} = \frac{\sum m_i r_i}{\sum m_i}$.

Position Vector of CM (Continuous Rigid Body)

The position vector of the center of mass for a single rigid body, given by $r_{CM} = \frac{\int r \, dm}{\int dm}$, where $r$ is the position vector of a differential mass element $dm$.

Hypothetical Negative Mass

A mathematical concept where mass $m$ or $dm$ is treated as negative to calculate the center of mass of bodies containing cavities or holes.

System Gravitational Potential Energy Change

The change in potential energy of a system of particles or bodies evaluated using the displacement of its center of gravity/mass: $\Delta PE = M g \Delta h_{cm}$.

Physics of Variable Mass Motion

The differential equation governing systems with varying mass over time, given by \sum F_{ext} = m \frac{dv}{dt} - v_{rel} \frac{dm}{dt}.

Center of Mass Frame (CM Frame)

A reference frame centered at and moving with the center of mass of a system, used to evaluate relative kinetic energy and momentum.