Ch 4Laws of Motion — Class 11 Physics, concept-first.

Force, in everyday language, is any push or pull that can start a body moving, stop a moving body, speed it up, slow it down, or change the direction in which it is travelling; a force can also change…

Newton's first law of motion states: a body continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by some external force acting on it.

Before stating Newton's second law, it helps to introduce the quantity it is actually written in terms of: linear momentum. The momentum of a body of mass moving with velocity is defined as

Many real forces -- a bat striking a cricket ball, a hammer striking a nail, one billiard ball colliding with another, an airbag decelerating a passenger -- act only for an extremely short interval of…

Newton's third law of motion states: to every action there is an equal and opposite reaction, or more precisely, whenever one body exerts a force on a second body, the second body simultaneously exert…

Consider an isolated system of two (or more) bodies on which no net external force acts -- meaning that any forces present are only the internal forces the bodies within the system exert on one anothe…

A free body diagram is a simplified sketch used to analyse the forces acting on one single, chosen body in a mechanics problem, in isolation from everything else around it. To draw one correctly:

Several forces are said to be concurrent when the lines along which they act all pass through one single common point, even though the forces themselves may point in entirely different directions.

Friction is the force that appears at the surface of contact between two bodies whenever one tends to slide, or actually slides, over the other, and it always acts along the contact surface, in the di…

Angle of friction. When a body rests on a rough surface at the point of limiting equilibrium (an applied force has just reached the value at which sliding is about to begin), the two separate contact…

A body moving in a circular path at a constant speed is said to undergo uniform circular motion. Even though its speed never changes, such a body is not moving with constant velocity, because velocity…

Building directly on the general result of Section 4.11 -- that circular motion at constant speed always requires a net inward (centripetal) force of magnitude , supplied by whatever real force fits t…

This section treats centrifugal force as its own dedicated topic, because it is one of the most commonly misunderstood ideas in the whole of circular-motion dynamics -- and the key to understanding it…

This chapter developed WBCHSE Unit 3's account of the laws of motion in the following order. Newton's first law defines inertia and identifies inertial frames.

Sample papers and previous-year board questions for this subject.