Newton's laws of motion- With Example/Physics

Newton's three laws of motion some of the basic principle of motion. Discuss and examples

     First Law: 

   Every object continues in its state of rest or of uniform motion in straight line if no need force acts upon it.

     And unwary passenger in a fast moving bus falls forward when it stops suddenly. This happens because the feet of the passenger come to rest suddenly whereas his body continuous to be in motion. In a head on collision between two vehicles, passengers are quiet often injured when they heat the wind screen. The collision stops the vehicle suddenly but the passengers continue their straight line motion in accordance with the first law and hence hit the screen.

     A person getting down from a moving bus has to run some distance, in the direction of the bus, before stopping. If he does not run he is bound to fall because his feet come to rest whereas his body continues to be in motion. 

   Before going on to the second law, it is necessary to understand momentum. The momentum of a body is divined as the product of its mass and velocity.

.    Momentum= mass x velocity.

   Second Law:

     The lost it's that " the rate of change of momentum of a body is proportional to the applied force and takes place in the direction of the force".

   It implies that force is professional to the product of mass and acceleration. If we express force (F) in newtons , mass(m) in kilograms and acceleration (a) in meters/ second ² , we can write the second law as

     F= m a

It is obvious that if the same force acts on 1 kg and 2 kg masses, the acceleration produced in the 1 kg mass will be twice of the produced in the 2 kg mass.

  In travelling the same distance, ek aur consumes mor fuel on a crowded road than on a free road. This happens because the car has to stop and start quite often on a crowded road. The repeated acceleration requires a force, which ultimately comes from the fuel. On a free road the car runs at almost uniform speed requiring fewer accelerations and hence less fuel consumption.

   Third Law:   

   This law states that " to every action there is an equal and opposite reaction". 

   The statement means that if body A exerts a force on a body B, then B exerts an equal and opposite force on A along the same line of action.

   Thus if a person strikes a wall with his fist, the force on the wall (action) is equal and opposite to the force on the fist (reaction) at the moment of impact.

   When a bullet is fired from a gun, equal and opposite forces are exerted on the bullet and the gun. Owing to action the bullet goes in the forward direction, and because of an equal and opposite reaction the gun experiences a recoil in the backward direction. 

  Rocket Propulsion: 

    A rocket contains solid chemicals which burn to produce a high velocity blast of hot gases. Space rockets have liquid fuel together with a supply of liquid oxygen to enable the fuel to burn. In either case, the large force created by chemical reaction propels out hot gases through the tail nozzle with a very high velocity. The reaction to this force propels the rocket forward. Though the mass of gases escaping per second is very small, their momentum is very large due to their tremendous velocity of escape. An equal and opposite momentum is imparted to the rocket which, despite its large mass, builds of a high velocity.

     Jet Engine:   

     The engine in a Jet aeroplane works on the same principle as a rocket but there is a difference in the method of obtaining the high velocity gas jet. The fool used in jet engine is paraffin. While rockets carry their own oxygen supply, jet engines draw air out of the atmosphere. Therefore, jet engines cannot be used to propel vehicles into outer space where there is no atmosphere.

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