DYNAMICS OF TRANSLATIONAL MOTION
§ 1 Newton's first law.
- Newton's 1 law
This law is called the law of inertia. Inertia - the body's ability to maintain speed. Inertial motion - motion with constant velocity.
An example of an inertial reference frame can serve as the heliocentric reference frame, i.e., the reference frame of the Sun.
Any system, moving relative to the heliocentric uniform rectilinear will be inertial.
The content of the 1st Newton's law reduced to two statements:
2) there are inertial frames of reference.
§ 2 Mass, momentum of the body.
Under the action of the body changes its velocity is not instantaneous, but gradually, i.e., acquires a finite acceleration, which is smaller, the greater the mass, that is, when exposed to the same forces
Density is the ratio of body mass dm small volume dV to the value of this volume
if the body is homogeneous, then ρ = const and
Center of mass, or center of mass system of particles is a point with a radius vector , which is equal to
Vector quantity equal to the mass m of a point on its velocity is called momentum (or linear momentum) of the material point
Momentum of the system is the vector of point , equal to the geometric sum (ie, the sum of the vectors) of all material points
Velocity of the center of inertia:
that is, the momentum of the system is equal to the mass of the entire system on the speed of its center of inertia.
If the body has several forces, under the force F in Newton's second law is necessary to understand the resultant force (net force) - geometrical sum of all forces acting on the body.
Vector quantity Fdt called the elementary impulse of forcer.
- 2-nd Newton's law –
the basic equation of the dynamics of the translational motion of a rigid body. The force acting on a body is equal to the mass of the body to its acceleration.
Tangent and normal acceleration determined by the appropriate component of the force F
Force Fn, which imparts at normal acceleration is directed towards the center of curvature of the trajectory and is therefore called the centripetal force.