Question

drive 2nd law of motion
clad 11

Answer 1

Suppose an object of mass, m is moving along a straight line with an initial velocity, u. It is uniformly accelerated to velocity, v in time, t by the application of a constant force, F throughout the time, t. The initial and final momentum of the object will be, p1 = mu and p2 = mv respectively.  The change in momentum ∝ p2 – p1 The change in momentum∝ mv – mu The change in momentum∝ m × (v – u). The rate of change of momentum ∝ m × (v −u)/t Or, the applied force, F ∝m × (v −u)/t F  = km (v -  u)/t F = kma  Here a [a = (v – u)/t ] is the acceleration, which is the rate of change of velocity. The quantity, k is a constant of proportionality.The SI units of mass and acceleration are kg and m s-2 respectively. The unit of force is so chosen that the value of the constant, k becomes one. For this, one unit of force is defined as the amount that produces an acceleration of 1 m s-2 in an object of 1 kg mass. That is, 1 unit of force = k × (1 kg) × (1 m s-2). Thus, the value of k becomes 1. and  F = ma which is the mathematical expression on the Newton's second law of motion.

Answer 2

Newton's second law of motion can be formally stated as follows: The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.