Newton’s Laws of MotionNewton’s Laws of Motion

11/5/1311/5/13

BellworkBellwork

What forces act on a projectile?What forces act on a projectile? Gravity Gravity Air ResistanceAir Resistance

Time for Make-Up WorkTime for Make-Up Work

Tues. 11/5Tues. 11/5 - Before school - Before school Wed. 11/6Wed. 11/6 – Before school and after school – Before school and after school

((NOTENOTE: no conference period): no conference period) Thurs. 11/7Thurs. 11/7 – Before school, conference – Before school, conference

period and after school period and after school

Force and Net ForceForce and Net Force

Force:Force: (Vector) A type of push or pull on (Vector) A type of push or pull on an object. an object.

Net ForceNet Force (Vector): The sum of all the (Vector): The sum of all the forces that act on an object. forces that act on an object.

Unit for Force: Newton (N = kg·m/sUnit for Force: Newton (N = kg·m/s22)) A Newton is a derived unitA Newton is a derived unit Derived units are made up of fundamental Derived units are made up of fundamental

unitsunits

Contact and Action at a Distance Contact and Action at a Distance ForcesForces

Contact forcesContact forces - forces that result when two - forces that result when two interacting objects are physically contacting interacting objects are physically contacting each other. each other.

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

Contact Forces Contact Forces Applied ForceApplied Force Surface ForceSurface Force Friction Force Friction Force Air Resistance Air Resistance

ForceForce Tension ForceTension Force Compression ForceCompression Force Spring ForceSpring Force

Action-at-a-Distance Action-at-a-Distance ForcesForces

Force of GravityForce of Gravity Electrical ForceElectrical Force Magnetic ForceMagnetic Force

Newton’s WorkNewton’s Work

In 1687 Newton In 1687 Newton wrote:wrote:

The PrincipiaThe Principia - - Mathematical Mathematical Principles of Principles of Natural Natural PhilosophyPhilosophy

Newton’s 1Newton’s 1stst Law of Motion Law of Motion

Lex I: Corpus omne perseverare in statu Lex I: Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis directum, nisi quatenus a viribus impressis cogitur statum illum mutare.cogitur statum illum mutare.

Law I: Every body persists in its state of Law I: Every body persists in its state of being at rest or of moving uniformly being at rest or of moving uniformly straight forward, except insofar as it is straight forward, except insofar as it is compelled to change its state by force compelled to change its state by force impressed.impressed.

Newton’s 1Newton’s 1stst Law of Motion Law of Motion

An object at rest stays at rest and an object An object at rest stays at rest and an object in motion stays in motion with the same in motion stays in motion with the same velocity unless acted upon by an unbalanced velocity unless acted upon by an unbalanced force. force.

This is BIG for the time!This is BIG for the time! The thought was an object in motion needed The thought was an object in motion needed

a force acting on it to keep it in motion.a force acting on it to keep it in motion.

Newton’s 2Newton’s 2ndnd Law of Motion Law of Motion

Lex II: Mutationem motus proportionalem Lex II: Mutationem motus proportionalem esse vi motrici impressae, et fieri secundum esse vi motrici impressae, et fieri secundum lineam rectam qua vis illa imprimitur.lineam rectam qua vis illa imprimitur.

Law II: The alteration of motion is ever Law II: The alteration of motion is ever proportional to the motive force impressed; proportional to the motive force impressed; and is made in the direction of the right line and is made in the direction of the right line in which that force is impressed.in which that force is impressed.

Newton’s 2Newton’s 2ndnd Law of Motion Law of Motion

If there is a net force on an object then If there is a net force on an object then the object will accelerate in the direction the object will accelerate in the direction of the net force depending on the mass of the net force depending on the mass of the object. 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 accelerationhigh mass = lower acceleration

Newton’s 3Newton’s 3rdrd Law of Motion Law of Motion

Lex III: Actioni contrariam semper et Lex III: Actioni contrariam semper et æqualem esse reactionem: sive corporum æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi.æquales et in partes contrarias dirigi.

Law III: Law III: To every action there is always To every action there is always opposed an equal reaction: or the actions of opposed an equal reaction: or the actions of two bodiestwo bodies upon each other are always upon each other are always equal, and directed to contrary partsequal, and directed to contrary parts..

Newton’s 3Newton’s 3rdrd Law of Motion Law of Motion

When one body exerts a force on a When one body exerts a force on a second body, the second body exerts second body, the second body exerts an equal and opposite force on the an equal and opposite force on the first.first.

TWO objects and TWO forces TWO objects and TWO forces Forces always come in pairsForces always come in pairs

A Reversed World AssignmentA Reversed World Assignment Write a 2 to 3 page (or 1-2 typed) science Write a 2 to 3 page (or 1-2 typed) science

fiction story describing what differences we fiction story describing what differences we would observe if the opposite of Newton's would observe if the opposite of Newton's three laws were true.three laws were true.

““A long time ago in a galaxy far, far A long time ago in a galaxy far, far away....” or “Once upon a time” type story.away....” or “Once upon a time” type story.

Need to use the opposites of each one at Need to use the opposites of each one at least once.least once.

Cite at the end where each one was used Cite at the end where each one was used and how/why this is an opposite law.and how/why this is an opposite law.

Due Wed. 11/13/12Due Wed. 11/13/12

A Reversed World AssignmentA Reversed World Assignment

11stst Law of Motion Law of Motion Opposite: An object at rest moves and Opposite: An object at rest moves and

objects in motion will change velocities objects in motion will change velocities randomly (increase, decrease or change randomly (increase, decrease or change direction).direction).

Example: objects will move with no force Example: objects will move with no force acting acting andand moving object will slow down moving object will slow down speed up or change direction for no reason.speed up or change direction for no reason.

A Reversed World AssignmentA Reversed World Assignment

22ndnd Law of Motion Law of Motion Opposite: To accelerate a massive object Opposite: To accelerate a massive object

you need a small force and to accelerate a you need a small force and to accelerate a small mass you need a large force.small mass you need a large force.

Example: To lift a massive boulder would Example: To lift a massive boulder would take no effort; to lift a pencil would take all take no effort; to lift a pencil would take all your strength.your strength.

A Reversed World AssignmentA Reversed World Assignment

33rdrd Law of Motion Law of Motion Opposite: You could put an object without Opposite: You could put an object without

being pushed back.being pushed back. Example: If a car pushed on the road, the Example: If a car pushed on the road, the

road would not push back. (think of a road would not push back. (think of a slippery surface)slippery surface)

A Reversed World AssignmentA Reversed World Assignment Write a 2 to 3 page (or 1-2 typed) science Write a 2 to 3 page (or 1-2 typed) science

fiction story describing what differences we fiction story describing what differences we would observe if the opposite of Newton's would observe if the opposite of Newton's three laws were true.three laws were true.

““A long time ago in a galaxy far, far A long time ago in a galaxy far, far away....” or “Once upon a time” type story.away....” or “Once upon a time” type story.

Need to use the opposites of each one at Need to use the opposites of each one at least once.least once.

Cite at the end where each one was used Cite at the end where each one was used and how/why this is an opposite law.and how/why this is an opposite law.

Due Wed. 11/13/12Due Wed. 11/13/12

Example of the 3Example of the 3rdrd Law Law