3.3. Weight. Newton's Second Law

Experience shows that by force free body changes the speed of its translational motion, gaining acceleration . In this case, the acceleration of the body is directly proportional to the force causing it and coincides with it in the direction:

Where - positive coefficient of proportionality, constant for each specific body.

The magnitude of the acceleration acquired by force , depends on the body, on which the force acts. Since it is more difficult for large bodies to impart acceleration than for small ones, it is customary to express proportionality between force and acceleration in the following form:

(3.2)

The proportionality coefficient m depends on the subject. Its value increases with increasing body size, if they are homogeneous. The constant m is called body mass. Mass is a measure of the inertia of the body in the outward motion. The smaller the inertia of the body, the greater the acceleration it must acquire under the action of a particular force. Thus, Newton's second law can be formulated as follows: the acceleration of the body is directly proportional to the force causing it, coincides with it in direction and inversely proportional to the mass of the body.