Newton's first law
-an object at rest will remain at rest; an object in motion will continue with the constant velocity unless forces acted upon it. this is called as the law of inertia.
Newton's second law
-according to Newton, an object accelerate if acted on by an unbalanced force. This acceleration depends on two factors.
1. the resultant force acting on the object, and
2. the mass or amount of matter of which the object is made.
The acceleration is directly proportional to the resultant force acting on the object's mass. If a group of forces act on an object of mass m. the vector of these forces F causes the object to have an acceleration a given by:
a= F/m or F = m a
the direction of a is in the direction of the resultant force.
Newton's second law is often written as F = m a. the force of F on the left side of the equation, however, represents the net or resultant force acting on the object.
Units for Newton's second law of motion
the unit of acceleration in SI system is the meter/second2 (m/s2). for the mass is the kilogram, and the force is the Newton(N)
1 N = (1 kg) (1 m/s2)
Newtons third law
for every force exerted is an equal oppositely directed force actong on some other body. this is often called the law of action and reaction
Newton indicated in this law that forcwa come in pairs. the action force is the force exerted by one object on another. the reaction force is the force exerted by the other object on the first.
Tension in a string
Tension in a srting is a particular case of Newton's third law of motion. this is back pulling or reaction exerted by a mass on the strong because of its resistance of motion.
Law of universal Gravitation
the gravitational force exerted by a mass m1 on a nother mass m2 is proportional to the product of their masses and the inversely proportional to the square of their separation r.
F = G m1 m2 / r2
where G is a constant called the universal gravitational constant equal to:
G = 6.6 x 10 Nm2 / kg2
Reaction:
Sir Isaac Newton first presented his three laws of motion in the "Principia Mathematica Philosophiae Naturalis" in 1686. His third law states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exerts an equal and opposite force on object A. Notice that the forces are exerted on different objects.
For aircraft, the principal of action and reaction is very important. It helps to explain the generation of lift from an airfoil. In this problem, the air is deflected downward by the action of the airfoil, and in reaction the wing is pushed upward. Similarly, for a spinning ball, the air is deflected to one side, and the ball reacts by moving in the opposite direction. A jet engine also produces thrust through action and reaction. The engine produces hot exhaust gases which flow out the back of the engine. In reaction, a thrusting force is produced in the opposite direction.
FOR EVERY ACTION, THERE IS AN EQUAL AND OPPOSITE REACTION
