Newton’s Laws of Motion 11/24/14

Force and Net Force Force: (Vector) A type of push or pull on an object. Force: (Vector) A type of push or pull on an object. Net Force (Vector): The sum of all the forces that act on an object. Net Force (Vector): The sum of all the forces that act on an object. Unit for Force: Newton (N = kg·m/s 2 ) Unit for Force: Newton (N = kg·m/s 2 ) A Newton is a derived unit A Newton is a derived unit Derived units are made up of fundamental units Derived units are made up of fundamental units

Contact and Action at a Distance Forces Contact forces - forces that result when two interacting objects are physically contacting each other. Contact forces - forces that result when two interacting objects are physically contacting each other. Action-at-a-distance forces - forces that result even when the two interacting objects are not in physical contact with each other, yet are able to exert a push or pull despite their physical separation. Action-at-a-distance forces - forces that result even when the two interacting objects are not in physical contact with each other, yet are able to exert a push or pull despite their physical separation.

Contact Forces Applied Force Applied Force Surface Force Surface Force Friction Force Friction Force Air Resistance Force Air Resistance Force Tension Force Tension Force Compression Force Compression Force Spring Force Spring Force Action-at-a-Distance Forces Force of Gravity Force of Gravity Electrical Force Electrical Force Magnetic Force Magnetic Force

Newton’s Work In 1687 Newton wrote: The Principia - Mathematical Principles of Natural Philosophy

Newton’s 1 st Law of Motion Lex I: Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare. Lex I: Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare. Law I: Every body persists in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed. Law I: Every body persists in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed.

Newton’s 1 st Law of Motion An object at rest stays at rest and an object in motion stays in motion with the same velocity unless acted upon by an unbalanced force. An object at rest stays at rest and an object in motion stays in motion with the same velocity unless acted upon by an unbalanced force. This is BIG for the time! This is BIG for the time! The thought was an object in motion needed a force acting on it to keep it in motion. The thought was an object in motion needed a force acting on it to keep it in motion.

Newton’s 2 nd Law of Motion Lex II: Mutationem motus proportionalem esse vi motrici impressae, et fieri secundum lineam rectam qua vis illa imprimitur. Lex II: Mutationem motus proportionalem esse vi motrici impressae, et fieri secundum lineam rectam qua vis illa imprimitur. Law II: The alteration of motion is ever proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed. Law II: The alteration of motion is ever proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed.

Newton’s 2 nd Law of Motion If there is a net force on an object then the object will accelerate in the direction of the net force depending on the mass of the object. If there is a net force on an object then the object will accelerate in the direction of the net force depending on the mass of the object. Same net force on an object: Same net force on an object: low mass = higher acceleration low mass = higher acceleration high mass = lower acceleration high mass = lower acceleration

Newton’s 3 rd Law of Motion Lex III: Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi. Lex III: Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi. Law III: To every action there is always opposed an equal reaction: or the actions of two bodies upon each other are always equal, and directed to contrary parts. Law III: To every action there is always opposed an equal reaction: or the actions of two bodies upon each other are always equal, and directed to contrary parts.

Newton’s 3 rd Law of Motion When one body exerts a force on a second body, the second body exerts an equal and opposite force on the first. When one body exerts a force on a second body, the second body exerts an equal and opposite force on the first. TWO objects and TWO forces TWO objects and TWO forces Forces always come in pairs Forces always come in pairs

Newton’s Laws Quick Summary 1 st Law: 1 st Law: An object at rest stays at rest An object at rest stays at rest An object in motion stays in motion with the same velocity, if no net force An object in motion stays in motion with the same velocity, if no net force 2 nd Law: 2 nd Law: Accelerations are do to the net forces on an object (mass) Accelerations are do to the net forces on an object (mass) 3 rd Law: 3 rd Law: Action and reaction pair of forces Action and reaction pair of forces