Important Terms and Definitions of Mechanics | Mechanics and SOM Exam points Lec-10 PDF

Important Terms and Definitions of Mechanics | Mechanics and SOM Exam points


1. Acceleration

The rate of change of velocity of body. [m/s²]
a= v-u
        t
Dimensions formula: [LT^‐²]


2. Linear Velocity [m/s]

It is the rate of change of the object's position with respect to time.
V= D/t


3. Radians

Measure of an angle [Theta(θ)]
θ= lenge of arc
        Radius 


4. Angular velocity

The angular velocity of an object is the angular displacement with respect to time.
Rate of change of angle with time.
The angular velocity, represented by ω.
ω = θ/t


5. Momentum

Momentum is the product of mass and velocity.


6. Moment

The tendency of forces is not only to move a body but also to rotate the body. This rotational tendency of a force is called moment.
M = Force × perpendicular Distance 
Unit: MKS: kg-m ; SI: N-m


7. Varignon's Theorem

If a number of coplanar forces are acting on a body then ∑M about a point in their plan is equal to the moment of their resultant about the same point.


8. Parallel forces

The force whose lines of action are parallel to each other are called parallel forces.

I. Like parallel force

It the forces, having lines of action parallel to each other, act in the same direction, then the forces are called like parallel forces.

II. Unlike parallel force

When the forces, having lines of action parallel to each other, act in opposite directions, they are called unlike parallel forces.


9. Couple

A couple is a pair of two equal and unlike parallel forces acting on a body in such a way that the lines of action of the two forces are not the same.
A couple is two equal forces which act in opposite direction on an object but not through the same point so they produce a turning effect.
Pair of equal parallel forces that are opposite in direction.
Turning effect: produce rotational motion.

Example of Couples:
(a) Opening or closing the cap of a pen.
(b) Opening or closing of a water rap.
(c) Winding of a watch.
(d) Moving the paddles of bicycle.
(e) Twisting a screw driver.
(f) Steering a mortar car.


10. Torque

It is also known as moment of a force.
The tendency of a force to rotate the body to which it is applied.
The moment of a couple is known as torque. [N-m]


11. Impulse

A force or movement of energy that causes a reaction.
I = Force × Time


12. Strength

Resistance to failure. [Material property]


13. Stiffness

Resistance to failure [secondary design property]


14. Kinetic energy

K.E= 1/2mv²


15. Potential energy

P.E= mgh


16. Thrust

Force or push acting on a body(or object) perpendicular to its surface and it's effect depends on the area on which it's acts.

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