Сформулируйте вопросы на английском языке и дайте ответы на них. Что такое импульс частицы? Сформулируйте законы сохранения энергии и импульса для системы частиц.
What is the momentum of a particle?
Momentum of a particle is the product of the mass and velocity of a particle.
where m – mass, v – velocity.
Formulate the laws of conservation of energy and momentum for a system of particles.
Law of conservation of energy for a system of particles: the total energy of the system of particles is costant? When this system is isolated (no external forces act on the system).
-
mechanical case, T
– kinetic, V
– potential energy.
Law of conservation of momentum for a system of particles: in an isolated system of particles the total momentum is constant.
For example, two particles interact. Because of Newton’s third law, the forces between them are equal and opposite.
;
.
Therefore:
or
-
case of two particles.
-
law of conservation of momentum.
Сформулируйте вопросы на английском языке и дайте ответы на них. Сформулируйте универсальный закон сохранения энергии. Выведите теоретически закон сохранения импульса.
Formulate the universal law of conservation of energy.
Energy can neither be created (produced) nor destroyed by itself. It can be only transformed from one form to another, but the total energy of an isolated system is always constant.
Derive theoretically the momentum conservation law.
According to the second Newton’s law for the system of N particles:
where 
momentum
of the system
and 
—
the
resultant of all the forces acting on particles of the system
Here 
—
the
resultant of the forces,
acting
on the n-th
particle
from side of m-
th,
and 
—
the
resultant of all external forces acting on
k-th
particle.
According
to the
third Newton's law, power type
and 
will
be equal to the absolute value and opposite in direction, i.e. 
.
Therefore,
the second sum in the right-hand part of the expression (1) is equal
to zero, we obtain that the derivative of momentum in the system over
time is equal to the vector sum of all external forces acting on the
system:
Internal forces are excluded by Newton's third law.
For systems of N particles in which the sum of all external forces is equal to zero
or
for systems, on the particles of which, no external forces act 
(for
all k from 1 to n),
we
have
As you know, if derivative from an expression is zero, the expression has a constant value with respect to the variable differentiation, so:
(constant
vector).
That is, the total momentum of the system of N particles, where N any integer, is a constant value.
Сформулируйте вопросы на английском языке и дайте ответы на них. Что называется гравитационной потенциальной энергией? Что называется кинетической энергией? Что такое вес тела?
What is called the gravitational potential energy?
Gravitational potential energy is energy an object possesses because of its position in a gravitational field.
For objects near the Earth the acceleration of gravity g can be considered to be approximately constant and the expression for potential energy relative to the Earth's surface becomes
where h is the height above the surface and g is the surface value of the acceleration of gravity.
What is called the kinetic energy?
In physics, the kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body in decelerating from its current speed to a state of rest.