Concept of Force

The push or pull which, when applied on an object, changes or tends to change (i) the state of rest, (ii) the state of uniform motion, or (iii) the shape and size of the object, measured in newton with dimension [MLT⁻²], is called Force.

The force which acts through direct physical contact between two objects, such as Frictional Force, Tensional Force, Normal Force, Air Resistance Force, Applied Force, and Spring Force, is called Contact Force.

The force which can act over distances without any physical contact between objects, such as Gravitational Force, Electrical Force, and Magnetic Force, is called Long Range or Non-contact Force.

The vector sum of all forces acting on an object is called Net Force.

The force of gravity on Earth which is always equal to the weight of the body, expressed as F_grav = mg where g = 9.8 m/s², is called Gravity Force.

The force which is exerted by a surface on a moving object or on an object making an effort to move, expressed as F_f = μ × F_N where μ is the coefficient of friction, is called Friction Force.

The support force exerted perpendicularly by a surface on an object in contact with it is called the normal force.

The force which is applied to an object by a person or another object is called applied Force.

The force transmitted by a string, rope, or wire when pulled tightly by forces acting from its ends, whose magnitude is the same everywhere in the rope, is called tension Force.

The force exerted by a compressed or stretched spring upon or by an object, expressed as F_spring = −kx (Hooke's Law), is called spring Force.

For two masses m₁ and m₂ connected by a string over a pulley:

1. Acceleration: a = \[\frac{(m_1-m_2)}{m_1+m_2}\] × g

2. Tension: T = \[\frac{2m_1m_2}{m_1+m_2}\] × g