Example of Statics and Dynamics
Physics / / July 04, 2021
Force concept: The action of pushing or dragging a body is called force. It is a vector quantity whose magnitude is the product of the mass and the acceleration. Its units are Newton (N), dynes (D).
N = kgm / s2
D = gcm / s2
The force formula is as follows:
fUEF = N
m = kg
a = m / s2
F = ma
EXAMPLE OF APPLICATION PROBLEM:
What is the mass of a body if, when a force of 18 N acts on it, it reaches a speed of 15 m / s in 2.4 S.?
We first determine the acceleration
a = v / t = 15 m / s / 2.4 s = 6.25 m / s2
Now we calculate the mass of the body
m = F / a = 18 N / 6.25 m / s2= 2.88 kg
Factors that change the structure or state of movement of objects: They are all those forces and concepts that are defined below.
Contact force: It is that friction force that is generated when a moving body collides with a static or resting body, a movement arising in this second body.
Ranged Force: It is that force that arises through the repulsion or attraction generated by a moving body towards another that is located at rest, which generates movement in this second body. For example, electric charges of the same sign repel each other, causing the body to move at rest.
Active forces: They are those forces of action found within a body in motion or at rest, which act to carry out a displacement.
Reactive forces: They are those reaction forces that act within a body when receiving an external force contrary to its movement or state of rest.
Weight of a body: It is equal to the gravitational force exerted by said body on the surface of the earth, in other words, it is the product of the mass of the body and the gravitational acceleration.
G = N
m = kg
g = 9.8 m / s2
G = mg
EXAMPLE OF WEIGHT OF A BODY:
Calculate the mass of a freely falling body with a weight of 4500 D.
m = G / g = 4500 D / 980 cm / s2= 4.59 g
Normal strength: It is the perpendicular force exerted to the trajectory by the support surface.
Friction force: It is the resistance that opposes the relative movement between two bodies. This type of force depends on the normal force and is regularly known as sliding friction and is due to the interaction between the molecules of the two bodies, it is sometimes called cohesion or adhesion depending on whether the bodies are the same or different material. The sliding friction force is
It opposes the movement of the body, therefore it has a direction opposite to the speed. Regularly the friction force is constant, so there are certain coefficients of friction.
The vector character of the force: Every force is represented by vector magnitudes, which are represented by means of an arrow in the Cartesian plane and to obtain the components it is required to know the following:
Direction of force: Line in which it moves, this can be east or west and / or the angle it forms with a horizontal x.
Sense of force: Where it goes up, down, left and right; It is represented by the head of the arrow.
Magnitude of displacement: It is the measure of scale chosen for the representation in the plane.
Force starting point: Place where the representation of the magnitude of the force will begin.