Lecture Notes - Mechanics

Lecture- 1 Lecture Notes by SSK 1  MECHANICS The branch of physics which deals with motion and effect of force on a body is called mechanics Lecture Notes by SSK 2  MECHANICS Newtonian mechanics are defined by the Newton's la...

Lecture- 1 Lecture Notes by SSK 1  MECHANICS The branch of physics which deals with motion and effect of force on a body is called mechanics Lecture Notes by SSK 2  MECHANICS Newtonian mechanics are defined by the Newton's laws of motion are three physical laws that describe the relationship between the motion of an object and the forces acting on it. Force is an external cause that changes or tends to change the state of rest or motion of any object Lecture Notes by SSK 3  MECHANICS the branch of physics which deals with motion and effect of force on a body is called mechanics  Classification of mechanics 1.Statics: The branch of mechanics which deals with bodies at rest under the action of system of forces is called statics. 2.Dynamics: The branch of mechanics which deals with moving bodies under the action of system of forces is called dynamics. Dynamics again has been divided into two parts viz. Kinematics and Kinetics. Lecture Notes by SSK 5  Classification of mechanics Dynamics again has been divided into two parts viz. Kinematics and Kinetics. Kinematics: The branch of mechanics which deals only with the nature of motion without having any regard to the cause of motion is called Kinematics. Kinetics: The branch of mechanics which deals with both the nature and causes of motion is called Kinetics. Lecture Notes by SSK 6  Rest and Motion Rest: When an object does not change its position in course of time with respect to its surroundings, then that state of the body is said to be at rest and the object is called stationary object. For example, houses, trees etc. are stationary object or bodies. Motion: When an object or an object changes its position in course of time with respect to its surroundings, then that state of the body is said to be in motion and the object is called moving object. For example, running men, trains, cars etc.. Lecture Notes by SSK 7  Nature of motion Translational motion/ Linear motion Rotational motion/ Circular motion Oscillatory motion Periodic motion Lecture Notes by SSK 8  Nature of motion One dimensional motion Two dimensional motion Three dimensional motion Lecture Notes by SSK 9  Measuring Motion: a Frame of Reference Frame of reference may be defined as a Frame of reference: coordinate system or set of axes within which position, orientation z and other properties of objects can (x, y, z) be measured. y O x We measure position relative to some fixed point O, called the origin. We give the ball’s location as (x,y,z) Lecture Notes by SSK 10  Parameters required for explain the One-Dimensional Motion Displacement: Distance in a particular direction units: meters (can be positive or negative) Velocity = rate of change of displacement, units: Meters per second, written m/s or m.sec-1. Acceleration = rate of change of velocity, units: Meters per second per second, written m/s2 or m.sec-2. Lecture Notes by SSK 11  Displacement & Distance Displacement: The distance moved in a particular direction is called displacement. So, both magnitude and direction is important here. It is denoted by the symbol ‘x’. It is a vector quantity. Its SI unit is meter (m). If the displacement Δx = x2 – x1, magnitude is written |Δx| = |x2 – x1|. Distance: The total length of the path traveled by a moving body in a particular time is called distance. It is denoted by the symbol‘s’. It is a scalar quantity. Its SI unit is meter (m). Lecture Notes by SSK 12  QUESTION What differs from distance and displacement? Direction Lecture Notes by SSK 13  Average Speed and Average Velocity Average speed = distance /time taken. Average velocity = displacement/time taken so average velocity is a vector! x2  x1  x Formula for average velocity: v  t2  t1 t Lecture Notes by SSK 14 Difference between Speed and Velocity Lecture Notes by SSK 15  Instantaneous Velocity If the time interval approaches zero, the rate of change of displacement with time is called instantaneous velocity or simply velocity. Mathematically, we write: x dx v  lim .  t0 t dt Lecture Notes by SSK 16  Acceleration Average acceleration = change in velocity/time taken v2  v1  v a t2  t1 t Velocity is a vector, so acceleration is a vector. Lecture Notes by SSK 17  Instantaneous Acceleration If the time interval approaches zero, the rate of change of velocity with time of a body is called the instantaneous acceleration or simple acceleration. The instantaneous acceleration v dv a  lim . t0 t dt Lecture Notes by SSK 18 s  vt some quantities like distance, displacement, speed, velocity and acceleration etc. These quantities are related to each other which are expressed by some equations. These equations are called Equations of motion Lecture Notes by SSK 19  Concepts from Newton’s Law’s of motion Lecture Notes by SSK 20  Newton’s First Law of Motion Every body continues in it’s state of rest or of uniform rectilinear motion except if it is compelled by forces acting on it to change that state. The concept comes from this law: Inertia Mass Force Lecture Notes by SSK 21 Inertia is the resistance of any physical object to any change in its state of motion. This includes changes to the object's speed, direction or state of rest. Lecture Notes by SSK 22  Mass The intrinsic property of an object. It is defined as the measure of the amount of matter in a body This mass of the object measures the object’s resistance to being accelerated: the object’s qualitative measure of inertia. It is denoted by m. Lecture Notes by SSK 23  Force Force is an external agent capable of changing a body’s state of rest or motion. It has a magnitude and a direction. The push or pull on an object with mass causes it to change its velocity. Lecture Notes by SSK 24 Force and Acceleration Lecture Notes by SSK 25 Momentum Lecture Notes by SSK 26  Newton’s Third Law If two bodies interact, the force on B from A is equal in magnitude to the force on A from B, and opposite in direction : FAB  FBA Lecture Notes by SSK http://startswithabang.com/?p=1718 27 Lecture Notes by SSK 28  Thank You! 29 Lecture Notes by SSK