Newtons Laws of Motion

Aristotle384-322 BC Four elements: earth, water, fire, airNatural vs Violent motionMotion on earth is straight Motion in the heavens is circular Earth centered universe

1People believe this for 2000+ yearsHe was wrong

Copernicus first person that said earth revolved around the sun

Galileo1564-1642 ADheavy and light objects fall together Sun centered universe Inertiathe speed at which objects fall doesnt depend on mass

http://www.youtube.com/watch?v=L55jImEhNZ0&feature=related

Dropping of feather and hammer on moon video

3No one believe Galileo

Newton1643-1727 ADInvented calculus 3 Laws of MotionInertia F=maAction/reaction

4While most people know what Newton's laws say, many people do not know what they mean (or simply do not believe what they mean). Well cover Newton 1You will have enough info to work through the first problem set after the next 10 slides.1st Law of Motion (Law of Inertia)

Inertia - the tendency of an object to resist a change in motion.

more mass = more inertia

The heavier something is, the more inertia it has.The best kick in the history of footballhttp://ed.ted.com/lessons/football-physics-the-impossible-free-kick-erez-garty What is mass? Weight = the force of gravity on an objectmeasured in newtons (N)Mass = amount of mattermeasure of inertiameasured in kilograms (kg)

not volume

not weight

9Mass is not volume

On Earth 2.2 lbs = 1 kg = 9.8 N

weight (N)gravity (m/s2)mass (kg)Ex) If Billy has a mass of 15 kg, what is his weight? weight = mass x gravity w =15 kg x 9.8 m/s2 w = 147 kg*m/s2 147 NTrue or False?The more mass something has the more inertia it has.The less inertia something has, the easier it is to change its motion.If something has a lot of inertia and is at rest, it is hard to move.It is difficult to change the motion of moving objects that have a lot of inertia.12

Inertia - the tendency of an object to resist a change in motion.more mass = more inertia

This is too true:1st Law

Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.

But once it is airborne, unless acted on by an unbalanced force (gravity and friction from the air) it would never stop!

Now can you explain this better?

What forces are involved?Donner (hair)HoffmannMcIntyreLudyWhy in everyday life do we observe objects in motion slowing down and stopping when we dont see any forces acting on them?

Its a force we sometimes cannot see friction.https://www.youtube.com/watch?v=C7NPD9W0kro Slide a book across a table and it will stop. The book comes to a rest because of the friction with the table.

In the absence of a force of friction, the book would continue in motion with the same speed and direction - forever! Static friction resistance that must be overcome to start an object in motion

Kinetic friction resistance between objects already in motionSliding friction: ice skatingRolling friction: bowlingFluid friction: air or water resistanceFriction force that resists motion of objects in contactFriction Force equationFf = Fnforce of friction (N)coefficient of friction (no units)normal force (N)Normal force force that balances gravity - always perpendicular to the surface

Net force combination of all the forces acting on an object

Fnet = 400 N

Fnet = 20 N no net force = no change its motion.

net force = the object will accelerate

Someone rolls a ball, after they let it go, what forces are acting on it? Fg = force of gravity Fn = normal force Ff = force of friction

FgFnFfExample ProblemAlex likes to slide through the kitchen in his socks. Alex weighs 850 N and the coefficient of sliding friction between his socks and the floor is 0.120. What is force of friction that opposes Alexs motion?

Ff = FnFf = .120 850 NFf = 102 NFgFnFf

Can be >1?Having a coefficient of friction higher than 1 isn't bizarre, it just means that it takes more force to slide something horizontally than it would to physically pick the object up. Coefficient of friction is a ratio of frictional force to gravitational weight, effectively.Minute to Win It

Newton's 1st Law

Minute to Win It Pre-Game:Can you demonstrate the Law of Inertia?Will the penny at rest, stay at rest?

Indicate the Mood:In this challenge the contestants will remove a piece of paper from the top of tippy test tubes to drop pennies into the tube. He/she will accumulate points based on the total # of pennies dropped into the tube during 1 minute.If you break the test tube you forfeit the challengeThis challenge will begin inhttps://www.youtube.com/watch?v=B3lLYOGDsts

2nd Law of Motion

The more force you apply to something the more its motion changes.

The more massive an object is, the bigger the force.

30Say your riding with a friend in their old beat up multi colored truck and it breaks down in the middle of the road. What do you do? Get out and push it. One person is steering and the other is pushing, but the one person can move the truck, they are weak, so you both push. Increase the force the truck starts moving, it accelerates. Direct relationship.

If the truck was more massive, how would the motion change? It wouldnt accelerate as much. Inverse relationshipNewtons 2nd Law

force (N)acceleration (m/s2)mass (kg)How much force is needed to accelerate a 1400 kilogram car 2 m/s2?F=?m=1400 kga= 2 m/s2F = m x aF = 1400kg x 2 m/s2F= 2800 kg*m/s2 or 2800 NCheck Your Understanding1. What acceleration will result when a 12-N net force applied to a 3-kg object? A 6-kg object?

2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass.

3. How much force is needed to accelerate a 66-kg skier 1 m/s2?

4. What is the force on a 1000-kg elevator that is falling freely at 9.8 m/s/s?

Check Your Understanding1. What acceleration will result when a 12-N net force applied to a 3-kg object? 12 N = 3 kg X 4 m/s2 12N = 6 kg x 2 m/s2 2. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass. 16 N = 3.2 kg x 5 m/s2 3. How much force is needed to accelerate a 66-kg skier 1 m/s/s?

66 kg-m/s2 or 66 N

4. What is the force on a 1000-kg elevator that is falling freely at 9.8 m/s/s.?

9800 kg-m/s2 or 9800 N

If you fell or if an elephant and a mouse each were to fall from the top of the Rib Mountain Tower at the same time, who would hit the ground first?

Newtons 2nd Law says:

F = m a

What have we neglected to consider?They are the same???36Imagine an elephant and a mouse falling through the air. The force pulling it down is the force of gravity, if the elephant has a mass of 1000 kg and we multiply its mass by 10 (round 9.8 up to simplify) then the Fg=10,000 N. Likewise the mouse with a mass of 1 will have a force of gravity pulling it down of 10 N. Therefore when we use Newtons second law to calculate their acceleration, they have equal acceleration at 10 m/s2 or 9.8 m/s2. This is true in free fall, but what did we neglect or take out to simplify things when we talked about free fall? Air resistance or drag. Now we are going to consider air resistance so we can talk about terminal velocity. Air Resistance:an object with a large cross-sectional area= fall slowertwo objects with the same area =lighter object would fall slower.

.

200 kgTerminal Velocity:

force of friction = force of gravity air resistance = weightacceleration = 0 m/s2 in F=ma, if the a = 0 m/s2Fnet = 0 N(FNET) = (FW - FD).

Who has a higher terminal velocity, a person who has a mass of 200 kg or a person with a mass of 100 kg?38Terminal velocity is the velocity reached when the drag force equals the weight of the body minus the buoyant force, which halts acceleration and causes speed to remain constant.

the terminal velocity of a skydiver in a normal freefall position with a closed parachute is about 120 mph or 54 m/s. This velocity is the asymptotic limiting value of the acceleration process, since the effective forces on the body more and more closely balance each other as it is approached. In this example, a speed of 50% of terminal velocity is reached after only about 3 seconds, while it takes 8 seconds to reach 90%, 15 seconds to reach 99% and so on

Gliding is a controlled fall.

Thorpe five-O IS BACK!!!She is practicing the fastest growing sport in Norwayhttp://www.youtube.com/watch?v=Nf2ENQRHKA4

Video Clip

Trig ReviewS O H C A H T O A

Free Body Diagrams - A picture that shows all of the forces acting on an objectWhat are the forces acting on this object?FfFnFg

Fp

http://lectureonline.cl.msu.edu/~mmp/applist/si/plane.htm

The problems can get complicated:

Example) A car of mass of 2000 kg is on an icy driveway inclined at an angle of 20.0, determine the force of the plane?What info does the problem give us?m=2000 kg= 20.0Fp= ?

Billy and his dad are sledding down the hill at an angle of 15.0. If their combined mass is 55.2 kg, what is the force pulling them down the hill?

Newtons 3rd LawBasically: For every action, there is an equal and opposite reaction.

JohnNickSuppose two carts, one twice as massive as the other, fly apart when the compressed spring that joins them is released. 1. How does the force exerted by the spring on the 1m-cart compare to the force exerted by the spring on the 2m-cart?

The forces are equal due to Newtons action/reaction law

2. How fast does the 2m-cart roll compared to the smaller 1m-cart?

It would roll half-as fast since it experienced half the acceleration when released from the spring.

NowWhat forces are involved in a tug of war?FgFnFfFpIts mainly about the friction with the floorAction / Reaction

52Have two students stand on the cart and grab the ends of a rope. Have only one student pull on the rope and observe that both move.

http://www.physics.uci.edu/~demos/mechanics.html Arnold Strongman and Suzie Small are having a tug of war contest. They pull on opposite ends of a rope. Who exerts a greater force on the rope?

Rope tension must be the same throughout the whole rope. Therefore, Arnold can pull no harder on the rope than Suzie. The most important factor in a tug of war is not how hard you pull on the rope, but how hard you push on the ground.

54http://www.physics.uci.edu/~demos/What gun and bullet would you want to be shot with?A gun with very little mass and a bullet with a lot of mass?

Or

A gun with lots of mass and bullet with very little mass?

Which will experience the greater acceleration, the car or truck if the forces are equal?

F = FM a = M aAction / Reaction

Fgun = FbulletMa = M aMinute to Win It

Newton's 3rd Law

Rolling LoverIn this challenge contestants Alex + Tyler and Amanda + Peyton will target a heart based on their personal momentum.He/she will sit on a skateboard and use the action of a partner to push them and the reaction of their movement should put them onto the target.This can be repeated (but always from behind the beginning line) to accumulate more points.This challenge will begin inhttps://www.youtube.com/watch?v=B3lLYOGDsts

59Definition summary:an object with a large cross-sectional = fall slowertwo objects with the same area =lighter object would fall slower. contradict Galileo?free fall: objects fall at the same rate with equal air resistance. only applies in a vacuum, where there is NO air resistance and drag is equal to zero.

LETS REVIEW:Look at your notes as this video plays to see if they agree.http://www.youtube.com/watch?v=s24jZwU0-RA (4min)

61Newtons Laws of Motion1st Law An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.2nd Law Force equals mass times acceleration.3rd Law For every action there is an equal and opposite reaction.Tension ForceTransmitted through a string, rope, cable, or wire Pulled tight by forces acting from opposite endsForce is directed along the length of the wire and pulls equally on the objects on the two opposite ends of the wire. cos =

Fg

FT

Fg / FT

Tension = stretching force in a rope

Demos with spring scalesThe tension in the rope can be broken down into its horizontal and vertical components. The vertical component of Ft has to equal the Fg.

Pressure (N/m2) or Pa Awl DemoBed of Nails Video inertia of cement block and area of nails http://www.youtube.com/watch?v=pGiLYt9clfQ Walking on Glass Demo

Force (N) Area (m2)length x width A man with a mass of 40 kg is ice fishing. The area of contact between the ice and the man is 0.20 m by 0.40 m. What pressure does the man exert on the ice?

71

Dont forget.Bernoulli

Bernoulli's Principle states that as the speed of a moving fluid increases, the pressure within the fluid decreases

73Chimney DemoApples Demo

Humans have dreamt of flight ever since they wondered how birds could fly.Daedalus and Icarus

History:https://www.youtube.com/watch?v=PsyqXbFAWJ0 74Icarus and Daedalus - An Ancient Greek LegendDaedalus was an engineer who was imprisoned by King Minos. With his son, Icarus, he made wings of wax and feathers. Daedalus flew successfully from Crete to Naples, but Icarus, tired to fly too high and flew too near to the sun. The wings of wax melted and Icarus fell to his death in the ocean.

Thrust moves an airplane, or bird, forward.

Thrust:Propeller

Thrust:Jet blast or rocket

Forces involved in the Bernoulli effect

Now look at the pictureTrust is forward but what force has to be overcome to achieve lift?Is it1. thrust2. weight 3. dragHold up your fingers.

Bernoullis Principal:Bernoulli's principle: as the velocity of a fluid increases, the pressure exerted by that fluid decreases = LIFTPut in notes

The velocities are higher at the upper surface than at the lower surface. The part of a timeline below the airfoil does not catch the one above. Write a complete sentence about each of these 6 topics in the video. This means 10-15 words per subject.-Daedalus and Icarus-kites-Leonardo da Vinci-balloons-gliders-insects

EYEWITNESS FLIGHT:https://www.youtube.com/watch?v=PsyqXbFAWJ0 83Icarus and Daedalus - An Ancient Greek LegendDaedalus was an engineer who was imprisoned by King Minos. With his son, Icarus, he made wings of wax and feathers. Daedalus flew successfully from Crete to Naples, but Icarus, tired to fly too high and flew too near to the sun. The wings of wax melted and Icarus fell to his death in the ocean.Teacher in lecture hall demos: http://www.youtube.com/watch?v=olVJzVadiFs