There are six fundamental principles of applied mechanics:
1. Stevinius Law for Combination of Forces
1. Stevinius Law for Combination of Forces
- They combine by Parallelogram Law.
- This law assigns the vector property to the forces.
2. Principle of Transmissibility
"The condition of equilibrium or motion of a rigid body will not be changed if a force acting at a given point of the rigid body is replaced by another force of the same magnitude and same direction acting on a different point along the same line of action."
Or, "The action of a force may be transmitted along its line of action."
Line of action of force: The line of action is an infinite straight line along which the force acts.
"The condition of equilibrium or motion of a rigid body will not be changed if a force acting at a given point of the rigid body is replaced by another force of the same magnitude and same direction acting on a different point along the same line of action."
Or, "The action of a force may be transmitted along its line of action."
Line of action of force: The line of action is an infinite straight line along which the force acts.
Here, forces F and F' have the same magnitude and they act along the same line of action. Thus, the two forces are equivalent.
"While the principle of transmissibility may be used freely to determine the conditions of motion of equilibrium of rigid bodies and to compute the external forces acting on these bodies, it should be avoided, or at least used with care, in determining internal forces and deformations."
3. Newton's Laws of Motion
First Law: Every particle continues in a state of rest or uniform in a straight line unless it is compelled to change that state by forces impressed on it.
Second Law: The change of motion is proportional to the force impressed and is made in a direction of the straight line in which the force is impressed.
Third Law: To every action there is an equal and opposite reaction.
This law refers to a system of particles or bodies in contact with each other and interacting.
4. Newton's Law of Gravitation
"While the principle of transmissibility may be used freely to determine the conditions of motion of equilibrium of rigid bodies and to compute the external forces acting on these bodies, it should be avoided, or at least used with care, in determining internal forces and deformations."
3. Newton's Laws of Motion
First Law: Every particle continues in a state of rest or uniform in a straight line unless it is compelled to change that state by forces impressed on it.
Second Law: The change of motion is proportional to the force impressed and is made in a direction of the straight line in which the force is impressed.
Third Law: To every action there is an equal and opposite reaction.
This law refers to a system of particles or bodies in contact with each other and interacting.
4. Newton's Law of Gravitation
"Two particles are attracted towards each other along the line connecting them with a force whose magnitude is directly proportional to the product of the masses and inversely proportional to the square of the distance between the particles."
Newton's Law of Gravitation introduces the idea of an action exerted at a distance and extends the range of application of Newton's Third Law: the action F and the reaction -F are equal and opposite, and they have the same line of action.