Common Forces In Mechanics - Practice Questions & MCQ

1. Gravitational force (Weight):-

• Definition- Force with which earth attracts an object.

• It always acts towards the center of the earth

• It is denoted by W=mg, where m=mass of the body and g= acceleration due to gravity.

2.    Normal Reaction(N ):-

• Definition- A contact force between two bodies in physical contact which acts perpendicular to common surface in contact.

• Normal reaction is always a push force

           Examples of Normal reaction acting on a block kept on horizontal surface and inclined plane is shown in figures below-

Examples of Normal reaction acting on a rod resting between ground and wall is shown in figures below-

3.    Tension(T):-

• Force exerted by taut string, rope or chain against pulling force along the length .

• It acts away from the point of contact.

• It is always a pull force

• Tension remains the same as long as the string is the same only in case of a massless string.

4.    Spring Force:-

• Spring force is a type of restoring force which tries to come back to its natural length.

• f = -Kx 

           where k is the spring constant and its unit is N/m and x is net elongation or compression in the spring.

• Here -ve sign represents the restoring nature of the spring force.