Force
* Force is an agent that tries, successfully or unsuccessfully, to move a body at restor to stop a moving body.
* A force can change the state of a body at rest, the state of motion of a body under motion, the direction of motion of a moving body or the shape of an object.
* The characteristics of force are magnitude, line of action, nature and point of application.
* Force is measured in newton in the SI system and in dyne in the CGS system.
* Force is a vector quantity.
* When a combination of forces is at work, the impact of these forces can be calculated through net force.
Net force is:
* The sum of all the forces acting on the body
* The single force that produces the same effects, which is produced on the body by the combination of the forces that act on the body
* When the net force is zero, forces are said to be balanced.
* When the net force is non-zero, forces are said to be unbalanced.
* Friction is the force resisting the relative motion of two bodies and act along the surface in contact.
First law of Motion
* Newton’s first law of motion states that an object will remain at rest, or continue to move at a constant speed in the same direction, unless an external force acts upon it.
* All objects resist a change in their state of rest or motion.
* Inertia is the tendency of undisturbed objects to stay at rest or to keep moving with the same velocity.
* Inertia is proportional to the mass of an object.
Momentum and Second Law of Motion
* Momentum (p) of an object is the product of its mass, and velocity: (p = mv)
* Newton’s second law of motion states that the rate of change of momentum of an object is proportional to the force applied on it and takes place in the same direction of the applied force.
F = ma
Where,
F is the applied force
m is the mass of the body
a is the acceleration
Impulse (J) is a large amount of force (F) action on an object for a short duration (t): (J = Ft)
Third Law of Motion
Newton’s third law of motion states that:
* When one object exerts a force on another object, the second object instantaneously exerts a force back on the first.
* These two forces are always equal in magnitude but opposite in direction, and form an action-reaction pair.
* These forces act on different objects, never on the same object.
* The essence of the third law of motion is that every action has an equal and opposite reaction.
* The law of conservation of momentum states that in the absence of any external force, the total momentum of the system is conserved.