* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Force and Newtons Laws
Survey
Document related concepts
Jerk (physics) wikipedia , lookup
Coriolis force wikipedia , lookup
Center of mass wikipedia , lookup
Fundamental interaction wikipedia , lookup
Newton's theorem of revolving orbits wikipedia , lookup
Equations of motion wikipedia , lookup
Relativistic mechanics wikipedia , lookup
Classical mechanics wikipedia , lookup
Fictitious force wikipedia , lookup
Modified Newtonian dynamics wikipedia , lookup
Rigid body dynamics wikipedia , lookup
Centrifugal force wikipedia , lookup
Classical central-force problem wikipedia , lookup
Transcript
Class Starter 1. If a car travels west 75 kilometers takes a uturn and travels back east 25 kilometers what is the car’s final displacement? 50 km west 2. If a car at rest, traveled north 5.5 s and reached a final velocity of 22.0 m/s, what was the car’s acceleration? 4.0 m/s2 3. If a force propels a car to move 300km in 4hrs what is the average speed (do not need to convert)? 75 km/h Ch 12 http://www1.teachertube.com/viewVideo.php?video_id=540&title=ForceMan_ WHAT IS A FORCE? – a push or a pull – one body exerts a force on another – SI units are Newton 2 (N), 1N=1kgm/s m = ( m )( a ) – F a Effects of forces on objects – Balanced forces – forces are equal in size & opposite in direction –Net force – force that changes the velocity of the object •Object accelerates in the direction of the greater force • A group of animals are playing tug-of-war. The elephants pull the rope with a force of 100N to the left. The donkeys pull the rope with a force of 105N to the right. Which way will the rope accelerate? • To the RIGHT Friction – A force that opposes motion between 2 surfaces that are touching each other Friction –Amount of friction depends on 2 factors 1. the kinds of surfaces (texture) 2. the force pressing the surfaces together (pressure) Four types of Friction 1. Static-friction force acts on objects that are NOT moving, acts in direction OPPOSITE to the applied force 2. Sliding-force opposes the direction of motion of object as it slides over a surface (less than static) Four types of Friction 3. Rolling-force acts on rolling objects (less than static or sliding) 4. Fluid-opposes motion of an object through a liquid/gas Gravitational Force • Gravity – the attracting force exerted by every object on every other object • Amount of gravitational force between objects depends on 2 things... Gravitational Force 1) mass a) more mass=more g force b) less mass=less g force 2) distance a) greater distance=less g force b) lesser distance=more g force ACCELERATION DUE TO GRAVITY Falling objects accelerate 2 at 9.8 m/s *same for ALL (in a vacuum w/ no air resistance) This means that for each s the body is falling, its velocity increases by 9.8 m per s Air Resistance • force air exerts on a moving object • Opposes gravity • Amount depends on: 1. Speed 2. Size 3. Shape 4.Density Terminal Velocity • The highest velocity that will be reached by a falling object • Downward Fg equals the upward Fair resistance Projectiles • Anything shot/thrown through the air • A thrown ball has constant horizontal velocity • Best angle to get farthest distance = 45O • Gravity pulls the ball downward • Vertical acceleration increases changing the direction of the projectile to forward and downward, making a curved path Projectiles Circles Centripetal Acceleration towards the center of a curved or circular path Circles Centripetal Force exerted toward the center of a curved path, w/out this force object will shoot off in a straight line in the direction it was traveling STAR Questions • List all 4 things that affect the amount of air resistance on an object. • Speed, size, shape and density • List the 2 things that affect the amount of friction btw 2 objects. • Texture and pressure • List the 2 things that affect the amt of gravitational force btw 2 objects. • Mass and distance Newton’s 1st Law • States an object moving at a constant velocity keeps moving at that velocity unless a net force acts on it. • If an object is at rest, it stays in rest unless a net force acts on it. • “If I push it, it goes” • Also called the law inertia of Inertia • Tendency of an object to resist any change in its motion • If an object is moving, it keeps moving at that speed & direction unless a force acts on it Inertia • The more mass an object has, the greater its inertia • More force would be needed to change the velocity of the object w/ greater inertia (which also means greater mass) Newton’s 2nd Law • The acceleration of an object is equal to the net force acting on it divided by the object’s mass • a=F/m or simply F=ma • amt of acceleration is affected by 1. size of the force F 2. mass of the object m a Thanks Cambridge Physics Outlet for amazing graphics! Examples: • What is the force required to push a 25kg girl in a 100kg wagon with an acceleration of 3m/s2? • Find the acceleration of an object with a mass of 20kg and a Force of 50N being applied to it? Mass • amount of matter in an object • constant independent of location • measured in g & Kg Weight • measure of force of gravity on an object Fg=W=mg • measured in Newtons (N) *g = 9.8m/s2 *Mass has to be in kg to calculate Weight Fg m g • What is the weight of a person who has a mass 50,000 g? • If a person has a mass of 50kg on Earth, would mass be less than 50kg on moon? • Would they weigh the same on the moon? Newton’s third law of motion • Whenever one object exerts a force on a second object, the second object exerts an equal & opposite force on the first object (action / reaction) • They do NOT cancel out because they act on different objects Thanks Cambridge Physics Outlet for amazing graphics! Momentum • More mass = More momentum • More velocity = More momentum • Momentum is transferred Law of conservation of Momentum • In a closed system, the loss of momentum of one objects equals the gain in momentum of another object – momentum is CONSERVED STAR Questions • What is the rate of acceleration due to gravity for a car? • 9.8 m/s2 • Describe Newton’s 1st law. • If I push it = it goes, if no push = no go • Describe Newton’s 3rd law. • Action = reaction