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### IMPORTANT DEFINITIONS AND CONCEPTS OF ENGINEERING MACHANICS

1. Displacement is defined as the distance moved by a body or particle in the specified direction.

2. The rate of change of displacement with time is called velocity.

3. Acceleration is the rate of change of velocity with respect to time.

4. The product of mass and velocity is called momentum.

5. A body is said to be treated as continuum, if it is assumed to consist of continuous distribution of matter.

6. A body is said to be rigid, if the relative position of any two particles in it do not change under the action of the forces.

7. Newton’s first law states that every body continue in its state of rest or of uniform motion in a straight line unless it is compelled by an external agency acting on it.

8. Newton’s second law states that the rate of change of momentum of a body is directly proportional to the impressed force and it takes place in the direction of the force acting on it.

9. Newton’s third law states for every action there is an equal and opposite reaction.

10. Newton’s law of gravitation states every body attracts the other body the force of attraction between any two bodies is directly proportional to their mass and inversely proportional to the square of the distance between them.

11. According to the law of transmissibility of force, the state of rest or motion of a rigid body is unaltered, if a force acting on a body is replaced by another force of the same magnitude and direction but acting anywhere on the body along the line of action of the replaced force.

12. The parallelogram law of forces states that if two forces acting simultaneously on a body at a point are represented by the two adjacent sides of a parallelogram, their resultant is represented in magnitude and direction by the diagonal of the parallelogram which passes through the point of intersection of the two sides representing the forces.

13. The qualitative description of physical variable is known as dimension while the quantitative description is known as unit.

14. A quantity is said to be scalar, if it is completely defined by its magnitude alone.

15. A quantity is said to be vector if it is completely defined only when it’s magnitude as well as direction are specified.