Newton's Laws of Motion

Newton's Three Laws of Motion

Newton's First Law of Motion:

                                               I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

Newton's Second Law of Motion:

                                               II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

                                        This is the most powerful of Newton's three Laws, because it allows quantitative calculations of dynamics: how do velocities change when forces are applied. Notice the fundamental difference between Newton's 2nd Law and the dynamics of Aristotle: according to Newton, a force causes only a change in velocity (an acceleration); it does not maintain the velocity as Aristotle held. 

                                               This is sometimes summarized by saying that under Newton,

                                       F = ma,

but under Aristotle

                                       F = mv, where v is the velocity.

                                                                               Thus, according to Aristotle there is only a velocity if there is a force, but according to Newton an object with a certain velocity maintains that velocity unless a force acts on it to cause an acceleration (that is, a change in the velocity). As we have noted earlier in conjunction with the discussion of Galileo, Aristotle's view seems to be more in accord with common sense, but that is because of a failure to appreciate the role played by frictional forces. Once account is taken of all forces acting in a given situation it is the dynamics of Galileo and Newton, not of Aristotle, that are found to be in accord with the observations.

Newton's Third Law of Motion:

                                             III. For every action there is an equal and opposite reaction.

                                                This law is exemplified by what happens if we step off a boat onto the bank of a lake: as we move in the direction of the shore, the boat tends to move in the opposite direction (leaving us facedown in the water, if we aren't careful!).

Mass and Weight

 Mass and Weight

                         Mass is defined as the measure of how much matter an object or body contains. It is measured in Gram (g). More the mass of object more is the gravitational force on the object. If we drop an object from a height, earth pulls it at the acceleration of 9.8m/s2

                            

                               Weight is the amount of force that earth exerts on us.

  

                                Acceleration is the rate of change of speed. This means speed of an object will increase by 9.8m every second. This means, if an object falls from a height to reach earth, after 10 second it would have achieve speed of 9.8 ×10 = 98 m/s. · Force causes acceleration, 

Sir Isaac Newton’s Second Law states that the acceleration (a) of an object is directly proportional to the force (F) applied, and inversely proportional to the object’s mass (m) Newton’s Second Law is usually summarized in equation form: 

 a = F/m, 

or F = ma 

Unit of force is derived as follows -

Unit of force F = m (Kg) × a (m/s2) 

                    = Kg m/s2 

                    = N 

To honor Newton’s achievement, the standard unit of force i.e kg m/s2 in the SI system is named as Newton (N). One Newton (N) of force is enough to accelerate 1 kilogram (kg) of mass at a rate of 1 meter per second square (m/s2). A kilogram is the amount of weight at which 1 N of force will accelerate at a rate of 1 m/s2. In practice, we measure weight, in terms of gms. or Kgs. But when weight is used as force, we must remember to measure it in terms of Newton.

Acceleration

Acceleration

        foot/second², meter/second², gal, galileo, inch/second²

i)  1 m/s² = 3.28084 ft/s²  
               = 100 cm/s²     
               = 39.37 inch per second squared (inch/s²) .

ii)  1 ft/s² = 0.3048 m/s²    
               = 30.48 cm/s²




iii)  1 g      = 9.80665 m/s²  
               = 32.17405 ft/s² 
                   = 386.1 in/s² 
                   = 35 kph/s 
               = 22 mph/s