10TH GRADE · CONSERVATION LAWS

Momentum and its conservation

Body impulse, force impulse and closed system.

22 minutes10 theory cards

LESSON MATERIAL

Basic Concepts

Closed system

A system of bodies, the external influence on which can be neglected in the problem under consideration.

The system boundaries are chosen so that the external impulse during the process is small. Then the interactions within the system do not change its total momentum.

Law of conservation of momentum

The total momentum of the closed system remains constant.

The vector sum of the impulses before the interaction is equal to the sum after it, if the external impulse can be neglected.

LESSON MATERIAL

Physical quantities

Body impulse

p

Vector measure of the mechanical motion of a body.

Unit: kilogram-meter per second · $\frac{\mathrm{kg}\cdot\mathrm{m}}{\mathrm{s}}$

Momentum change

\Delta p

The difference between the final and initial impulses.

Unit: kilogram-meter per second · $\frac{\mathrm{kg}\cdot\mathrm{m}}{\mathrm{s}}$

Time lapse

\Delta t

The duration of the force.

Unit: second · $\mathrm{s}$

LESSON MATERIAL

Lesson formulas

Body impulse

\vec{p}=m\vec{v}

Momentum is equal to mass times velocity.

Pulse unit

[p]=1\,\frac{\mathrm{kg}\cdot\mathrm{m}}{\mathrm{s}}

Impulse is measured in kilogram meters per second.

Force through change in momentum

F=\frac{\Delta p}{\Delta t}

Force is equal to the rate of change of momentum.

Impulse force

F\Delta t=\Delta p

The impulse of force is equal to the change in the momentum of the body.

Conservation of momentum of two bodies

m_1\vec{v_1}+m_2\vec{v_2}=m_1\vec{v_1}\prime+m_2\vec{v_2}\prime

The total momentum of two bodies before interaction is equal to the total momentum after it.

Condition: The system is closed or the impulse of external forces can be neglected.

Related formulas

Body impulsep · kg m/s

PRACTICE

Tasks on the topic

Conservation laws10 class · 17 problems