Falcon Focus What number do you get when you multiply all of the numbers on a telephone's number...

transcript

Falcon Focus• What number do you get when you multiply all What number do you get when you multiply all

of the numbers on a telephone's number pad? of the numbers on a telephone's number pad? • Essential Question: A snail was traveling across A snail was traveling across

a sidewalk. A brilliant physics student decided a sidewalk. A brilliant physics student decided to find the snail’s speed and so she found a to find the snail’s speed and so she found a ruler and a stopwatch. Is the student going to ruler and a stopwatch. Is the student going to find the snail’s average speed or instantaneous find the snail’s average speed or instantaneous speed? Explain.speed? Explain.

Agenda

• FF• EQ• Recognition of Motion Graphs and

Interpretations Race• Work on Packets• Ticket out the door• Closure

Tuesday

• Falcon Focus: What always goes to What always goes to bed with its shoes on?bed with its shoes on?

• Essential Question: How does friction How does friction affect an object’s motion?affect an object’s motion?

Describes how fast an object is moving.

Average Speed =distancetime

Velocity The speed of an object in a certain direction.

Velocity

V = velocity (meters/second)d = distance (meters)t = time (seconds)

d V = tspeed of an object in a certain direction.

Velocityspeed of an object in a certain direction.

seconds

Scalar a measurement that does NOT contain direction. Egg sample: Speed

Vectora measurement that contains

direction.Egg sample: Velocity

2 Volunteers

• Socks vs. Shoe Friction Demontration

Questions

• does it make a difference sliding in socks? does it make a difference sliding in socks? explain.explain.

• • Is it easier or harder on carpet than wood or Is it easier or harder on carpet than wood or

tiles?tiles?• • how do you think friction affects motion how do you think friction affects motion

based on what you observed?based on what you observed?

• Standard 8-5.3. Analyze the effects of forces (including gravity and friction) on the speed and direction of an object.

What is a force?

• A force is a push or pull

Types of Forces

• 1. Gravity• 2. Friction

• Forces such as gravity and friction can affect the speed and direction of an object.

Friction

• Friction is a force that occurs when one object rubs against another object.

• Friction is the Force that one surface exerts on another surface when they are moving across each other.

• Friction will cause a moving object to slow down and finally stop.

• Two factors determine the amount of friction –

• (1) the kinds of surfaces, and • (2) the force pressing the surfaces

together. (how hard the surfaces are pushed together during the motion )

– The slowing force of friction always acts in the direction opposite to the force causing the motion.

– Friction Opposes motion• Examples: rubbing hands together, gym

sneakers allowing you to stop better on the gym floor (compared to dress shoes)

• Friction can also be the force that makes it difficult to start an object moving.

• Enough force must be applied to a

nonmoving object to overcome the friction between the touching surfaces.

• The smoother the two surfaces are, the less friction there is between them; therefore, the moving object will not slow down as quickly.

– Friction between surfaces can be reduced, in order for objects to move more easily, by smoothing the surfaces, using wheels or rollers between the surfaces, or lubricating/oiling the surfaces.

– If friction could be removed, an object would continue to move.

• The greater the force pushing the two surfaces together, the stronger friction prevents the surfaces from moving.– As an object gets heavier, the force of friction

between the surfaces becomes greater.– To move a heavy object, a greater force must

be applied to overcome the friction between the surfaces.

Less or More Friction

Less or More

Friction Lab

• Title: Car Friction Lab• Problem: How does the texture of the tracks

affect the speed of the cars? • Explanation: Today you experiment on different

types of textures to see how friction affects its motion.

Closure

• Friction Lab Conclusion/TOD

• HOW DID FRICTION AFFECT THE HOW DID FRICTION AFFECT THE CARS' RACING TIMES?CARS' RACING TIMES?

• • why is friction considered a force? why is friction considered a force?

Wednesday

• Falcon Focus: What two things can What two things can you never eat for breakfast?you never eat for breakfast?

• Essential Question: Essential Question: How does mass How does mass and distance affect gravity?and distance affect gravity?

Family Guy Video

• What is gravity? What is gravity? • • Why is gravity considered a Why is gravity considered a

force?force?

Gravity (force that pulls objects down)

• Gravity is a force that always attracts or pulls objects toward each other without direct contact or impact.

• Gravity is a force of attraction, or a pull, between objects.

• Gravity pulls objects down.• Do gravity affects everything? ____________

• Gravitational attraction depends on the mass of the two objects and the distance they are apart.

• Objects on Earth are pulled toward the center of Earth.

• The force of gravity, like all other forces, can cause changes in the speed of objects.

• As an object falls, its speed will continually increase as Earth’s gravity continually pulls it downward.

• Gravity can also cause an object that is thrown into the air to change its upward motion, slow down, and fall back toward Earth’s surface.

• The pull of Earth’s gravity keeps the Moon in orbit; the moon is constantly changing direction because of gravity.

How Does Mass Affect Gravity?

• Imagine an elephant and a cat. Because the elephant has a larger mass than the cat does, gravity between the elephant and Earth is larger. So, the cat is much easier to pick up than the elephant. The gravitational force between objects depends on the masses of the objects.

• Objects with Larger or Heavier Mass has a larger gravitational attraction?

• Objects with a smaller mass has a smaller gravitational attraction.

How Does Distance Affect Gravity? • The mass of the sun is 300,000 times bigger than that of Earth.

However, if you jump up, you return to Earth every time you jump rather than flying toward the sun. If the sun has more mass, then why doesn’t it have a larger gravitational pull on you?

• This is because the gravitational force also depends on the distance between the objects.

• As the distance between two objects gets larger or further, the force of gravity gets much smaller.

• And as the distance between objects gets smaller or shorter, the force of gravity gets much greater.

• Although the sun has tremendous mass, it is also very far away. This means that it has very little gravitational force on your body or on small objects around you. The sun does have a large gravitational force on planets because the masses of planets are very large.

Air Resistance

• When air resistance is ignored, all objects will speed up at the same rate as they fall.

• What is air resistance? Air resistance opposes the downward motion of a falling object.

• Any falling object meets air resistance.

Questions

• WHAT TWO THINGS DETERMINE WHAT TWO THINGS DETERMINE GRAVITATIONAL FORCE? GRAVITATIONAL FORCE?

• • do all objects have a gravitational do all objects have a gravitational

force? explain your answer.force? explain your answer.•

Center of Gravity Lab

• “BET YOU CAN’T BALANCE” CHALLENGES* • Use what you've learned about balance to compete

with your friends and family with following balance challenges.

• HERE WE GO!!!!!!• http://nanaimoscience.org/wp-content/uploads/2014/

04/Playground-Physics1.pdf

Questions• IS THERE MORE GRAVITATIONAL FORCE BETWEEN IS THERE MORE GRAVITATIONAL FORCE BETWEEN

OBJECTS WITH SMALL MASSES OR OBJECTS WITH OBJECTS WITH SMALL MASSES OR OBJECTS WITH LARGE MASSES? LARGE MASSES?

• • THE SUN IS MUCH MORE MASSIVE THAN EARTH. WHY THE SUN IS MUCH MORE MASSIVE THAN EARTH. WHY

IS THE FORCE OF GRAVITY BETWEEN YOU AND THE IS THE FORCE OF GRAVITY BETWEEN YOU AND THE SUN SO MUCH LESS THAN EARTH’S GRAVITY AND YOU? SUN SO MUCH LESS THAN EARTH’S GRAVITY AND YOU?

• • HOW DOES AIR RESISTANCE AFFECT AN OBJECT’S HOW DOES AIR RESISTANCE AFFECT AN OBJECT’S

MOTION?MOTION?

• STUDY FOR QUIZ

THURSDAY

• FALCON FOCUS: There was a window cleaner who was There was a window cleaner who was cleaning a window on the 25th floor of a skyscraper. He cleaning a window on the 25th floor of a skyscraper. He suddenly slips and falls. He has no safety equipment and suddenly slips and falls. He has no safety equipment and nothing to soften his fall, but he is not hurt at all. How do you nothing to soften his fall, but he is not hurt at all. How do you account for that?account for that?

• ESSENTIAL QUESTION: ESSENTIAL QUESTION: HOW DOES MASS HOW DOES MASS AND DISTANCE AFFECT GRAVITY?AND DISTANCE AFFECT GRAVITY?

QUIZ TIME

INTRO TO CAR PROJECT

CLOSURE

FRIDAY

• FALCON FOCUS: what is in the what is in the middle of the sky?middle of the sky?

• ESSENTIAL QUESTION: ESSENTIAL QUESTION: How would How would you explain the difference between you explain the difference between balance and unbalance forces?balance and unbalance forces?

DEMONTRATION TIME !!

• ARM WRESTLING

QUESTIONS

• Explain balanced forces. How do they Explain balanced forces. How do they affect the motion of an object? affect the motion of an object?

• • Explain unbalanced forces. How do they Explain unbalanced forces. How do they

affect the motion of an object? affect the motion of an object?

Force and Mass

• 8-5.4 Predict how varying the amount of force or mass will affect the motion of an object.

• • Varying the amount of force or mass will

affect the motion of an object.

Force: A Push or Pull

• If an object is in motion and more force is applied to it, the object will begin moving faster.

• If two objects have the same mass and a greater force is applied to one of the objects, the object which receives the greater force will change speeds more quickly. For example if a ball is hit harder, it will speed up faster.

Forces

• If an object must be slowed down quickly, the force applied to the object must be greater than what is needed for a gradual slowing down. For example, the greater the force applied to the brakes of a bicycle, the more quickly it will slow down or stop.

Forces

• Varying the amount of force applied to a moving object can also change the direction that the object is moving more or less quickly. For example, a baseball pitched toward the batter may quickly change direction and speed if hit very hard, or may change direction and speed more slowly if hit softly as with a bunt.

• What is Mass?• Mass is the amount of matter in an object.

• What is matter?• Matter is anything that has mass and

volume.

• If a heavy (more massive) object is in motion, more force must be applied to get the object moving faster.

• If the same force is applied to two objects, the object with the smaller mass will change speeds more quickly. For example if a baseball and a bowling ball are thrown with the same force the baseball will speed up faster.

• In order to slow down or stop a heavier (more massive) object, the force on that object must be greater than for a less massive object. For example, if the same braking force is applied to a small car and a large truck, the car will slow down more quickly.

• It is more difficult to change the direction of a heavy moving object, than one that is lighter in mass.

What is the difference between weight and mass?

WEIGHT MASS• Weight is a measure of the force gravity on

an object • Weight is a force• (Weight varies according to the

force of gravity pulling on you) Therefore, Your weight will vary depending on your location (On top of a mountain vs. being at sea level.

• Weight can change

• Amount of matter in an object

• Mass is not a force

• Mass is the same anywhere on Earth

• Mass is constant

Closure

• What 2 things can affect the motion of an object?

• What is the difference between weight and mass?

• What is force?• What is the relationship between force and

Flash Back Quiz

1. Name the 3 types of rocks and the location where they form.2.What process a rock would have to go through in order to become an igneous rock?3.What process a rock would have to go through in order to become a metamorphic rock?4.What process a rock would have to go through in order to become a sedimentary rock?5.Name and explain the 2 types of igneous rocks.

• 8-5.5 Analyze the resulting effect of balanced and unbalanced forces on an object’s motion in terms of magnitude and direction.

Forces

• Forces have a magnitude (strength) and a direction. (The unit for Force is Newton (N)

Forces

• Forces can be represented as arrows with the length of the arrow representing the magnitude or strength of the force and the head of the arrow pointing in the direction of the force.

• Using such arrows, the resulting force (net force) and direction can be determined.

Balance vs. Unbalance Forces

• Forces acting on an object can be balanced or unbalanced.

Balance Forces

• Balanced forces will cause no change in the motion of an object. (No Movement)

• Balanced forces acting on an object in opposite directions and equal in strength, as shown in the arrows below, do not cause a change in the speed/magnitude or direction of a moving object.

Balance Forces

• Objects that are not moving will not start moving if acted on by balanced forces. – For example, in arm wrestling where there is no

winner, the force exerted by each person is equal, but they are pushing in opposite directions. The resulting force (net force) is zero.

•• 5N 5N

Balance Forces

– Or, in a tug of war, if there is no movement in the rope, the two teams are exerting equal, but opposite forces that are balanced. Again, the resulting force (net force) is zero.

• • 5N 5N

Unbalanced Forces

• Unbalanced forces are not equal, and they always cause the motion of an object to change the speed and/or direction that it is moving.

Unbalance Forces

• When two unbalanced forces are exerted in opposite directions, their combined force is equal to the difference between the two forces. – The magnitude and direction of the net force

affects the resulting motion. – This combined force is exerted in the

direction of the larger force.

Unbalance Forces

– For example, if two students push on opposite sides of a box sitting on the floor, the student on the left pushes with less force (small arrow) on the box than the student on the right side of the box (long arrow). The resulting action (net force: smaller arrow to the right of the =) shows that the box will change its motion in the direction of the greater force as shown below:

•• 5N 10N 5N

Unbalance Forces

• Or, if in a tug of war, one team pulls harder than the other, the resulting action (net force) will be that the rope will change its motion in the direction of the force with the greater strength/magnitude as shown below:

• • 5N 10N 5N

Unbalance Forces

• If unbalanced forces are exerted in the same direction, the resulting force (net force) will be the sum of the forces in the direction the forces are applied.

Unbalance Forces

• For example, if two people pull on an object at the same time in the same direction, the applied force on the object will be the result of their combined forces (net force or longer arrow to the right of the =) as shown below:

• 5N + 10N = 15N

Unbalance Forces

• When forces act in the same direction, their forces are added. When forces act in opposite directions, their forces are subtracted from each other.

• Unbalanced forces also cause a nonmoving object to change its motion

Balance vs. Unbalance Forces

• If there is no net force (balance force) acting on the object, the motion does not change . If there is net force (Unbalance force) acting on an object, the speed of the object will change in the direction of the net force.

When the net force is Zero.-> NO movement

When the net force is NOT Zero.-> movement

2 Kg ?

Static Equilibrium Balanced forces When all forces are balanced. The net force is Zero. There is NO movement.

Inertia

• 8-5.6 Summarize and illustrate the concept of inertia.

Inertia

• Inertia is the tendency of objects to resist any change in motion. Inertia is a property of the object; it is not a force.

Inertia

• It is the tendency for objects to stay in motion if they are moving or to stay at rest if they are not moving unless acted on by an outside force.

Inertia

• The more mass an object has, the harder it is to start it in motion, to slow it down or speed it up, or to turn it.

• In other words, the more mass an object has, the more inertia it has.

The greater the mass the harder it is to move. And . . .the harder it is to stop moving.

Lower mass objects are easier to move . . .and to stop moving.

NEWTON’s Laws 1st Law of Motion :

An object remains at a

in a ,until a net force acts on it.

constant speed straight path

ih ner shahAn object willremain at a

constant speed (unless

disturbed).

NEWTON’s 1st Law of Motion is the law of

Examples of the effects of inertia might include:

• Inertia causes a passenger in a car to continue to move forward even though the car stops. This is the reason that seat belts are so important for the safety of passengers in vehicles.

• • Inertia is the reason that it is impossible

for vehicles to stop instantaneously.

Examples of the effects of inertia might include:

• Inertia is the reason that it is harder to start pushing a wheelbarrow full of bricks than to start pushing an empty wheelbarrow. The filled wheelbarrow has more mass and therefore, more inertia.

• • Inertia is also the reason that it is harder to stop a loaded

truck going 55 miles per hour than to stop a car going 55 miles per hour. The truck has more mass resisting the change of its motion and therefore, more inertia.

Flash Back Quiz

Closure

Homework

Gravity balancedUN

Time (mSec)Sp

) BALL

Ground

Inertia balancedUN

Time (mSec)Sp

PUTTER

Friction balancedUN

Time (Sec)Sp

Friction the resistive force that occurs

when two surfaces travel past each other.

causes physical deformationgenerates heat

Friction the resistive

force that occurs when two surfaces contact each other.

Oliver the dog doesn't want to walk in the rain. He can make his owner pull harder on the leash to

get him out the door by

sitting on the vinyl floor. sitting on the tile floor.

sitting on the carpeted floor. sitting on the wood floor.

Pauline needs to measure the sliding friction of a brick. How should she go about doing this?

attach the brick to a string and then to a spring scale and read the force needed to quickly lift the brick off the ground

drag the brick by a string attached to a spring scale so that it gradually speeds up

drag the brick by a string attached to a spring scale along the surface of a table at a constant speed and read the force

hang the brick from a string attached to a spring scale and read the force

terminal velocity gravity will accelerate an object until air resistance (friction) does not allow it to go any faster.

In the absence of air resistance, which of these objects will fall at the fastest rate when dropped?

the ball with a mass of 75 kg

They all fall at the same rate.

Gravitational force

Gravitational forceo INCREASES with Masso DECREASES with Distance

All objects in the universe are attracted to each other by the force of

effort.

friction.

gravity.

inertia.

Four pairs of objects have the masses shown below. If the objects in each pair are the same distance apart, the gravitational force between the objects in which pair is greatest?

1 kilogram and 1 kilogram

1 kilogram and 2 kilograms

2 kilograms and 1 kilogram

2 kilograms and 2 kilograms

As an astronaut travels from Earth to a space station orbiting Earth, what happens to her mass and weight?

Her mass decreases, but her weight remains the same.

Her mass increases as her weight decreases.

Her mass remains the same, but her weight decreases.

Her mass decreases and her weight also decreases.

Which hill would you slide down the fastest?

hill A

hill B

hill C

It would take the same time to slide down all of the hills.

Projectile Motion

seconds

Velocity (m/s)forward downward

050 9.819.629.439.2

Projectile Motion

seconds

Velocity (m/s)forward downward

050 9.819.629.439.249 48 47 46

Falcon Focus What number do you get when you multiply all of the numbers on a telephone's number...

Documents