NCERT Solutions for Class 11 Physics Ch-4: Laws of Motion

Answer: Newton's second law states that the rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction of the force. Mathematically, F = dp/dt, which for constant mass simplifies to F = ma, where m is mass and a is acceleration.

Answer: Impulse is defined as the product of force and the time interval for which it acts, J = F × Δt. According to the impulse-momentum theorem, impulse equals the change in momentum of the object, J = Δp = m(v - u).

Answer: Newton's third law states that for every action, there is an equal and opposite reaction. For example, when a person jumps off a boat, they push the boat backward (action) while the boat pushes them forward (reaction) with equal magnitude but opposite direction.

Answer: The coefficient of friction (μ) is the ratio of the limiting frictional force to the normal reaction force between two surfaces. Static friction acts on an object at rest and prevents it from starting to move, while kinetic friction acts on an object already in relative motion and opposes that motion; static friction is generally slightly greater than kinetic friction.

Answer: Banking of roads at curves provides a component of the normal force directed towards the centre of the curve, which contributes to the required centripetal force. This reduces dependence on friction alone, allowing vehicles to negotiate the curve safely even at higher speeds without skidding.