|
Читайте также: |
| center of masses varying mass composite body | — — — | центр мас змінна маса составное тіло | launching pad fuel exhaust product | — —— | пускова установка паливо вихлопні гази |
The linear momentum of a particle is vector 
, defined as
in which mi is the mass of the particle and 
is its velocity. (The adjective linearis often omitted, but it serves to distinguish from angularmomentum, which is associated with rotation.) Note that since m is always a positive scalar quantity, and 
are in the same direction.
According to the first law of dynamics velocity of a material point has constant value and direction. In classic mechanics mass is constant, and consequently, momentum of a material point is also constant. Thus it is possible to say:
Momentum of the isolated material point is always constant
If 
then 
is constant.
Let’s consider a system of twoparticles. According to the third law of dynamics for two particles it looks like:
, or 
.
Therefore, the total momentum of the system of two material points is constant:
.
Дата добавления: 2015-11-16; просмотров: 86 | Нарушение авторских прав
| <== предыдущая страница | | | следующая страница ==> |
| AFTER STUDYING THE TOPIC A STUDENT IS TO | | | Total momentum of two interacted isolated material points is always constant |