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External and internal forces. One should distinguish between forces as external or internal with reference to
any particular body. Those forces acting on a given body which are exerted by other bodies are referred to as
external forces. Forces exerted on one part of the body by other parts of the same body are called internal
forces.
Graphical representation of forces. Vectors. Suppose we are to slide a box along the floor by pulling it with
a string or pushing it with a stick. That is, we are to slide it by exerting a force on it. For concreteness let us as-
sume the magnitude of the push or pull to be
10 lbs. It should be noted that simply to write “10 lbs” on the diagram would not completely describe the force,
since it would not indicate the direction in which the force was acting. If we represent a force by an arrow
called a vector, the length of the arrow, to some chosen scale, will indicate the size or magnitude of the force,
and the direction in which the arrow points will indicate the direction of the force.
Quantities like force and velocity, which involve both magnitude and direction, are called vector quantities.
Those like density, which involve magnitude only, are called scalars.
Composition of forces. When a number of forces are simultaneously applied at a point, it is found that the
same effect can always be produced by a single force having the proper magnitude and direction. We wish to
find this force, called the resultant, when the separate forces are known. The process is known as the composi-
tion of forces, and is evidently the converse problem to that of resolving a given force into components.
When two or more forces are to be combined, one may first find the resultant of any two, and then combine
this resultant with a third, and so on.
Vector difference. The resultant of two vectors is also referred to as their vector sum, and the process of
finding the resultant is called vector addition. In many instances, as when computing accelerations or relative
velocities, it is necessary to subtract one vector from another or to find their vector difference.
II. Translate the summary of the text into English.
Название текста – «Сила». Цель статьи – дать читателю представление о данном понятии. Физиче-
ский термин «сила», используемый в механике, обозначает толчок или напряжение. Обычно тело, кото-
рое проявляет силу, взаимодействует с телом, на которое данная сила направлена. Силы данного вида
известны как взаимодействующие силы. Автор приводит примеры взаимодействующих сил: сила мус-
кулов, сила пружины, а также сила сжатого воздуха на стенки сосуда. Силы бывают внутренние и
внешние. Сила и скорость составляют векторные величины. На точку может воздействовать как одна
сила, так и множество сил. Если объединить две и более сил, то можно сначала найти результат любых
двух сил, затем объединить полученный результат с третьей и т.д. Статья заканчивается описанием век-
торной силы.
III. Compare the original and the translation. Which techniques have been used in the translation ?
WHAT IS FORCE ?
The push or pull that
starts an object moving is a
force. Forces not only make
things move,
they can also speed up or
slow down а moving object,
make it change direction, or
even distort its shape. Gener-
ally, the stronger the force, the
greater the effect it has on an
object.
Толчок или натяжение,
которые приводят объект в
движение, называются си-
лой. Силы не только приво-
дят объекты в движение, на-
зываются силой. Они также
могут ускорить или замед-
лить движущийся объект
заставить его изменить на-
правление движения или
даже исказить его форму.
Вообще говоря, чем больше
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