INTRODUCTION-
A magnet can attract an iron nail form a distance, which shows that external agencies of force(gravitational and magnetic force)can exert force on a body even form a distance. vector sum of the force which acting on body is called net force.
Force– It is an external agency(push or pull) which change the position or state of an object. Its dimension is [M1L1T-2] and SI unit is Newton(N).
THE LAW OF INERTIA–
Galileo studied motion in inclined plane and conduct some experiment. He conclude that an object moving on a frictionless horizontal plane must neither have acceleration nor retardation ,that means it move with constant velocity. Also the term Inertia first introduced by Galileo
Law of Inertia -It state that an object will remain at rest or move at a constant velocity in a straight line unless acted upon by an external force.
If the net external force is zero, a body a rest continuous to remain rest or remain in motion. This property of body is called its Inertia. Inertia means ‘resistance to change‘. It is measured as the how much force required to change the state of body.
NEWTON S’ FIRST LAW OF MOTION-
Newton built on Galileo ‘s ideas and laid the foundation of mechanics in terms of three laws of motion .
First Law Of Motion- Every body continues to be in its stares of rest or of uniform motion in a straight line unless compelled by some external force to act otherwise. First law of motion also called law of Inertia.
If the net external force on a body is zero, its acceleration is zero. Acceleration can be non-zero, only if there is a net external force on the body.
Applications of Newton First law of motions- Water in glass(spills when abruptly stopped or started), In Trains and Buses(passengers lurch forward or backward with motion change), book on Dashboard(slides when car accelerated or stop suddenly) etc.
NEWTON ‘S SECOND LAW OF MOTION-
SECOND LAW OF MOTION-It state that the rate of change of momentum of a body is directly proportional to the external force applied on the body and the change takes place in the direction of applied force.
Momentum (p)– It is a product of mass(m) and velocity(v). p=mv and it referred to the second law of motion. It is vector quantity. It SI unit is kgm/s, and [M1L1 T-1].
Impulse (I)–It is product of average force and time taken(or change in momentum).I=F*t, Its SI unit is Kgm/s or N-s and dimension is [M1L1 T-1].
Applications of Newton Second Law of Motion-Kicking a ball(ball accelerate based on applied force), Bat hitting a ball(force on ball changes it acceleration and speed) etc.
NEWTON ‘S THIRD LAW OF MOTION-
Third Law Of Motion- To every action, there is a always an equal and opposite reaction .Both action and reaction never cancel each other because both act on different body. The force is always occur in pair. That means FAB =-FAB.
Applications of Newton Third Law of Motion- walking, Running, Boating, Summing etc.
CONSERVATION OF MOMENTUM-
The law of conservation of momentum states that the total momentum of a closed system(isolated system) remains constant if no external forces act on it. The total momentum of an isolated system of interacting particles is conserved. That means P’A+P’B=PA+PB . Conservation of momentum theorem is applicable for Fext=0, it does not depend on internal forces.
Application of conservation of momentum –
i). When a bullet fired from a gun, the gun recoil and give a kick in backward direction, then the equation is v=-mv/M, where v is velocity, m is mass of bullet and M is mass of gun.
ii). Rocket also work on this conservation of linear momentum.
EQUILIBRIUM OF A PARTICAL-
In mechanics it refer to the situation when net external forces of particle is zero. The resultant of any two forces say F1 and F2, obtained by the parallelogram law of forces must be equal and opposite to the third force F3. That means F1+F2+F3=0, this condition is called equilibrium condition.
FRICTION-
Friction – When a body moves or tends to move over the surface of another body, a forces comes into play which act as a parallel to the surface of of contact and opposes the relative motion. Its magnitude is equal to applied force and its unit is Newton(because it is also a type of force).
Types of friction -3
i). Static Friction( fs)-Force of friction which come into play between two bodies before one body actually starts moving over the other. It opposes the impending motion(motion take place under applied force, if friction is absent). It is self adjusting force and if no force then no static friction. It is directly proportional to the normal force(perpendicular to surface of friction)
ii). Kinetic Friction(fk)-Force that opposes relative motion between surfaces in contact is called sliding or kinetic friction. It depend on the nature of surfaces.
iii). Rolling Friction(fr)-Force of friction that come into play when a body rolls over the surface of another body. Rolling friction is much lesser than sliding friction.
Advantage of friction-help in walk, swim, hold, throw, protect the tyre of vehicle from slip, etc.
Disadvantage of friction-It produce heat in machines and it cause more fuel consumption and also reduce working capacity of machine, etc.
Method to reduce friction-By using lubricant, machine oil, by using gears, bearing, grease etc.
Angle of friction- Angle in which the resultant of limiting and normal reaction male with the normal reaction. tan α=μ.
Angle of repose- Angle of inclined plane at which a body placed on just began to slide. tan α= f/R = μ, where R is normal reaction, μ is coefficient of angle of repose.
CIRCULAR MOTION-
Circular Motion-When a body cover a definite circular path with constant velocity but its direction change continuously is called circular motion and there is a change in velocity of body the body and hence undergoes an acceleration, called centripetal acceleration or radial acceleration.
According to newton ‘s first law, every body require some force to come in motion or in rest, this external force is called centripetal force(FC ). FC=mv2/r and also FC=mrω2 where FC is centripetal force ,m is mass, r is radius, is omega respectively.
When a body move on level road– When a vehicle move on curved path ,then the wheel of vehicle has tendency to leave the curved path and again come straight path. The force between the tyres and road provide centripetal force which require to keep car in motion around the curved path. There are 3 forces act, weight of car mg, normal reaction R, and frictional force F. And there is no acceleration vertically then, R=mg
After derivation(in question) we get Vmax=√μsrg, where Vmax is maximum velocity for level road, μs is coefficient of static friction between tyres and road, r is radius, g is gravitation constant.
When a body move on banked road– The path in which raising the outer edge of a curved road above its inner edge is called banking of the curved road and the angle which the outer edge of a curved road is raised above inner edge is called angle of banking. Let us consider the weight of body is mg, the radius of curved road is r with velocity v and road banked at an angle θ. Also there is 3 forces acting on a body weight of car mg, normal reaction R, and frictional force F.
After derivation(in question section) we get the maximum velocity of a body is Vmax=√rg(μs+tanθ) / (1-μstanθ) for banked road, where Vmax is maximum velocity for banked road, μs is coefficient of static friction between tyres, road, r is radius, g is gravitation constant and road banked at an angle θ.
These all are the notes of chapter 4 in physics. And after some time you get important questions and NCERT solutions HERE. *#THANKS FOR VISITING, VISIT AGAIN#* 😊