Newton’s Laws of Motion - 1

Describes the relationship between the motion of objects in our everyday world and the forces acting on them. Conditions when Classical Mechanics does not apply: - Very small objects (< atomic sizes) - Objects moving near the speed of light Classical Mechanics

Forces Simple definition: a force is a push or pull on some object. Force is a vector quantity.

Distunguish: contact forces and remote (“action at a distance” or “field” forces. Contact forces result from physical contact between two objects. Field forces act between disconnected objects.

Examples of Contact and Field Forces

The Four Fundamental Forces In order of decreasing strength: Strong nuclear force Electromagnetic force Weak nuclear force Gravity All are field forces. Only gravity and electromagnetic forces are treated in classical mechanics.

Lex 1: Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare. Law 1: Every body continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it.

This is sometimes called the law of inertia.

Lex II: Mutationem motus proportionalem esse vi motrici impressae, et fieri secundum lineam rectam qua vis illa imprimitur. The acceleration produced by a particular force acting on a body is directly proportional to the magnitude of the force and inversely proportional to the mass of the body.

Lex II: Mutationem motus proportionalem esse vi motrici impressae, et fieri secundum lineam rectam qua vis illa imprimitur. The acceleration produced by a particular force acting on a body is directly proportional to the magnitude of the force and inversely proportional to the mass of the body.

Second Law: 1. The acceleration vector is in the direction of the net force. 1.

Second Law: 2. The magnitude of the acceleration vector is proportional to the magnitude of the net force. 2.

Second Law: 3. The magnitude of the acceleration vector is inversely proportional to the mass. 3.

The SI unit for force: The force that gives an object of 1 kg mass an acceleration of 1 m/s 2 is defined as 1 newton (N). 1 N = 1 kg. m/s 2