NCERT Solutions for Class 11 Physics Chapter 4 Laws of Motion

Newton’s laws are usually expressed in terms of the mass of a point or a particle, that is, an object of negligible volume. It is a reasonable approximation of real objects when the movement of internal parts is negligible and when the distance between objects is much larger than the size of each object. For example, the Earth and the Sun can be approximated as points when the orbits of the former around the latter are taken into account, but not when animals active on their surfaces are taken into account.

The mathematical description of motion or kinematics is based on the idea of specifying a position using numerical coordinates. The simplest case is one-dimensional, that is, when the object is constrained to move only in a straight line. Its position can then be given by a number indicating its position relative to a chosen reference point.

For example, if an object can slide freely along a track that runs left to right, its position can be specified by its distance to a convenient zero point, or by a negative number for position relative to the elevator and a positive number for the position at the elevator origin. Motion is represented by a function that assigns a values of all position coordinates to each value of the time variable.

Newton’s second law of motion applies to the behavior of all existing force imbalances. The second law states that the acceleration of an object depends on two variables, the resultant force acting on the object increases and the acceleration of the object increases. Increasing the mass of the object with decrease the acceleration.

The momentum of an object is equal to the product of its mass and its velocity, and momentum-like velocity is a vector that has both magnitude and direction. The force exerted on an object can change the amplitude of the momentum or its direction. Newton’s second law is important tools for almost all the chapters of class 11 physics. For objects of constant mass m, it can be written in the form F = ma, where F and a are both vector quantities. If an object is subjected to a resultant force, it will accelerate according to the equation. Conservatively, if an object is not accelerated, no net force acts on it.

A force is a pushing or pulling force acting on an object due to its interaction with another object. Force results from interactions. According to Newton’s third law of motion, whenever bodies A and B interact, they exert a force on each other. If we sit somewhere on any object, our body exerts a downward force. At the same time the object exerts an upward force on our body.

This law represents a certain symmetry in nature. Forces always come in pairs, and one object cannot exert a force on another without feeling the force itself. We sometimes loosely call this law the action-reaction force, where the force applied is the force of action and the force experienced as a result is the force of reaction.

For example, a swimmer uses his feet to accelerate the wall of the pool in the opposite direction he is pushing. The wall exerts equal and opposite forces on the swimmer. You might think that two equal and opposite forces would cancel each other out, but they don’t because they act on different systems. In this case, two types of systems can be studied: bathers or walls.