You are going home from school you travel 4 miles, you decide to stop at the mall which is another 4 miles, then you grab dinner at Taco Bell which is.

Do now

You are going home from school you travel 4 miles, you decide to stop at the mall which is another 4 miles, then you grab dinner at Taco Bell which is 2 miles away. The trip takes you

2 hours. What is the average speed of your trip?

Field trip on Wednesday. Please make sure that you are having your forms signed.

I.D. Badges Sophie Quiz as homework this week. Gone Friday, Monday, and Tuesday

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Into Forces House of cards Friction Friction Lab

Agenda

A force is simply a push or a pull (unit of measurement is a Newton or N).

All forces have both direction and size Any time there is a change in acceleration this means that the change was caused by a force.

What is Force?

We’ve been naming lots of forces lately. Gravity, friction, inertia are all examples.

Not all forces causes an object to move. For example you are all sitting on chairs, this exerts a force, but you do not cause the chair to move by sitting on it.

You also cannot see all forces, like the force of gravity or the force that attracts two magnets.

What is a force?

1. A force is a push or a pull? 2. You can see all forces? 3. Forces always cause an object to move?

True or False

Usually more than one force is acting on an

object. The NET FORCE is the combination of all the forces acting on an object.

If Brett and Chris are trying to move a piano and Brett pushes the piano with 25 N of force and Chris pulls the piano in the same direction with 20 N of force what is the net force?

Net Force

Forces can also go in different directions. For examples two students pulling on a rope, each trying to win it. The two students are pulling in different directions.

Carnell pulls the rope with 10 N of force to the right and Julian pulls with 12 N of force to the left? What is the net force and who wins the rope?

Opposite Force

When the forces of an object produce a net force of 0N, then the forces are BALANCED FORCES.

Balanced forces will not create a change in motion of an object.

Some examples of balanced forces are a hat sitting on your head, a birds nest resting in a tree, or a light bulb hanging from the ceiling

Balanced Force

When the net force is ANYTHING other than 0 then the force is UNBALANCED.

For example the tug-a-war between Carnell and Julian was an unbalanced force.

Unbalanced forces are necessary to move an object.

Unbalanced Force

Using the deck of cards at your table you and your table should work together to build a house made of cards that stands up on its own. By doing this you will have to balance out your forces so the house does not tip over and cause motion.

Build a balanced force

What stops a ball from rolling across the room forever and ever?

The force is called FRICTION. Friction is a force that opposes motion between two surfaces that are in contact.

Friction causes the ball to slow down and eventually stop. Friction is the reason your car stops when your parents slam on the brakes.

Friction

Friction occurs because the surface of any object is rough.

Even surfaces that feel smooth are filled with microscopic hills and valleys that make them rough.

So when two surfaces come in contact these “hills and valleys” stick together and make the objects slow down.

The heavier the object the more force that is exerted on the object and more friction.

Which would have more friction a 2lb book or a 5lb book?

Friction

Kinetic Friction is moving friction. For example rolling or pushing an object produces kinetic friction.

Do you think its easier to push a chair or roll it? Which would have more friction?

Kinetic Friction

Static friction is the friction of an object that is not moving. The object does not move because the force of static friction balances the force being applied to it.

If you were to get up and push the wall would it move? Why not? What type of friction?

Static Friction

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Phonebook Friction