third law of motion

We all have watched rockets flying either on TV or for real in sky ! A rocket is a missile or a vehicle which obtains thrust by the reaction of the rocket to the ejection of fast moving fluid exhaust from a rocket engine. Rockets work on Sir Isaac Newton’s Third Law of Motion, which states,For every action there is an equal and opposite reaction. A rocket is a type of reaction engine that moves forward when mass is thrown backward.

third law of motion

thrid law of motion

second law of motion

Acceleration is produced when a force acts on a mass.

The greater the mass (of the object being accelerated) the greater the

amount of force needed (to accelerate the object).
nWhat does this mean?

Everyone unconsiously knows the Second Law.

Everyone knows that heavier objects require more force to move

the same distance as lighter objects.

friction

Generally speaking wind speed increases with height above the surface as the frictional force of surface diminishes with height.

The friction imposed on air mechanically slows the wind and diverts its direction. The friction layer is the layer of air that is influenced by friction caused by the surface. The friction layer varies in height across the Earth, but for the most part lies within about a kilometer of the surface.

friction

A breakthrough in the exploration of friction on the atomic scale has recently become possible by means of friction force microscopy (see figure). The tip of an AFM-cantilever is brought into contact with an atomically flat surface, which moves with a constant speed v along the x-axis. The resulting torsion of the cantilever is observable by optical techniques, yielding the time resolved lateral force F(t) and its time average (effective friction force) as the quantity of foremost interest. From the dependence of this force on the sliding velocity v, the normal force FN, or the temperature T, one tries to gain insight into the specific molecular properties of the probed surface and into the general microscopic principles of surface friction within an exceptionally simple "minimal" system.

Newton's law of motion

because the Earth exerts a force on the stone and according to the universal law of gravitation, the stone also exerts an equal force on the Earth. Now the question is why we do not see the Earth moving towards the stone.