Unit 2 Lesson 2: Vectors, Equilibrium,Support Force,&Friction

​Science Root of the Day:

DO NOW: Write what you think the example words mean in your lab manual.

Extra Credit: Find three additional words that use this root and write them and their definition in your lab manual (6 Points Max)

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Vectors, Equilibrium, Support Force, & Friction

Multiple Choice

Which variable goes on the X-Axis of a graph?

• Dependent Variable
• Independent Variable
• Control Group
• Constants

Multiple Choice

What is a force? 

• combination of all forces acting on an object

• is a push or a pull on an objcet

• when life is stable

• is an arrow that represents the magnitude and direction of a quantity

Multiple Choice

Knowledge about the natural world that is based on facts learned through experiments and observation.

• quantitative observation

• experiment

• science

• scientific theory

• qualitative observations

Multiple Choice

An object's resistance to its change in motion is its

• Friction

• Inertia

• Gravity

• Pressure

Multiple Choice

Categorizing something or someone into a certain group or system based on certain characteristics is called....

• classifying

• predicting

• inferring

• experimenting

Multiple Choice

What kind(s) of objects have inertia?

• all objects with mass

• only objects at rest

• only objects in motion

• only objects whose motion is being changed

Lesson Objectives

• Be able to draw and interpret force vectors

• Be Able to Distinguish between Force and Net Force

• Understand how Equilibrium affects Force

• Define the Support Force and Friction

Net Force

• A force is any push or pull on an object

  • Multiple forces can exist at one time

• Net Force: The Total Force acting on an object

  • We show forces as arrows

    • Vector Quantity: a measurement that has both a magnitude (aka amount) and an direction

Working with Vectors

• A vector is drawn as an arrow that indicates the direction of a force

  • In general: We treat the right as positive and left as negative

  • Up is positive and down is negative

• We Try to draw Vector arrows to scale

Working with Vectors Sample Problem 1

• Your friend sitting to the right of you asks if they can borrow your text book You slide the book towards them with a force of 3 N. What is the net force of the book?

  • Step One: Draw your "object" that is experiencing force

    • Just draw a box to model your object

  • Step Two: Draw Vectors for all the forces

    • Include both Magnitude and direction

  • Step Three: Add all Vectors together

Working with Vectors Sample Problem 2

• Your friend sitting to the right of you asks if they can borrow your textbook You slide the book towards them with a force of 3 N. As the book travels, it hits your water bottle which pushes back on the book with a force of one newton. What is the net force of the book?

  • Step One: Draw your "object" that is experiencing force

    • Just draw a box to model your object

  • Step Two: Draw Vectors for all the forces

    • Include both Magnitude and direction

  • Step Three: Add all Vectors together

Multiple Choice

What is the sum of all forces acting on an object and direction?

• Net Force

• Balanced Force

• Unbalanced Force

• Applied Force

Dropdown

The net force acting on the box is ​

Select answer

​

Select answer

.

Multiple Choice

Which statement describes a vector?

• It has magnitude but no direction

• It has direction but no magnitude

• It has both direction and magnitude

• It has constant magnitude but no
   direction

Multiple Choice

What is the net force pulling on the cart and in which direction?

• 3 N Right

• 5 N Right

• 5 N Left

• 8 N Left

Multiple Choice

What is the net force on the box?

• 10 N Right

• 10 N Left

• 2 N Left

• 0 N

The Equilibrium Rule

• Let's say you hang a bag on a spring scale

  • Gravity pulls the bag downward, but the spring pulls the bag upwards

    • Tension: A stretching Force

  • Both are pulling in opposite with the same amount of force, so the bag doesn't move

• Equilibrium: When the Net force on an object is equal to zero

  • ΣF = 0

Equilibrium of Moving Objects

• Equilibrium only means that there is no change in the force on an object

  • This can occur both when an object is at rest, as well as when an object is moving at a constant speed in one direction

• Static Equilibrium: Equilibrium where an object is at rest

• Dynamic Equilibrium: An Equilibrium that occurs when an object moves in a straight line at a constant speed

The Support Force

• A book lying on a desk is at equilibrium

  • What Forces Are Acting on the Book?

    • Gravity is pushing the book down, so why is the book not moving towards the floor?

  • Something is pushing up to counteract the force of gravity?

• The Support Force: an upward force exerted on an object

  • Also Called the Normal Force

Multiple Choice

Equilibrium means....

• being at rest

• traveling at light speed

• balance

• pushing or pulling

Multiple Choice

What does this mean?

• sum of forces equals zero

• everyone forget physics

• Billy and Bob will be falling 140 ft and 110 ft respectfully

• Billy and Bob's effective faith in their balance is zero

Drag and Drop

For an object at rest on a horizontal surface, the ​

Placeholder

  must equal the object's weight.

Drag these tiles and drop them in the correct blank above

Net Force

Support Force

Force

Equilibrium

Multiple Choice

True or False: The object pictured is in Static Equilibrium and will remain still?

• True

• False and it will move downward

• False and it will move upward

• False and it will move to the right

• False and it will move to the left

The Force of Friction

• Friction: A force that opposes motion or attempted motion

  • From the Latin word fricare- to rub

  • Acts opposite the force of motion

    • If motion is to the right, friction is to the left

    • Is the force that eventually stops an object from moving

The Force of Friction

• Friction can occur between all states of matter

• Air Resistance: The Force of Friction experienced when moving through the Air

Factors that Affect Friction

• There are two factors that affect how the force of friction works

  • The type of surfaces involved

    • A smoother surface has less friction than a rough one

  • How hard the surfaces are pushed together

    • A heavier object experiences more friction because it is pushing harder against the ground

Different Types of Friction

• Whenever two objects physically interact, there is some form of friction

• There are 4 different types of friction

  • Sliding Friction

  • Static Friction

  • Fluid Friction

  • Rolling Friction

Sliding Friction:

• Occurs when two solid objects slide across each other

• Makes objects slow down and stop

Static Friction:

• Acts between two solid objects that are not moving

• A force that stops movement from happening

  • Think about moving a heavy couch.

    • You need to push very hard to move it

Fluid Friction

• Occurs when a solid object moves through a fluid material

  • Liquid or air

• Is easier to overcome than sliding friction

Rolling Friction

• Occurs when an object rolls across a surface

• Is much easier to overcome than sliding friction

  • Only a small portion of the object is in contact at any given time

Friction is Universal

• Our fingers have ridges on them to help us grip objects

  • Bumps make it harder for objects to slide over something

• In many instances, we want to decrease friction to make movement more efficient

Match

Match the following Types of Friction to their descriptions

• Static Friction

• Slide Friction

• Fluid Friction

• Rolling Friction

Pushing a stationary car

Sledding down a hill

A plane flying through the air

A skateboarder going down a ramp

• Pushing a stationary car

• Sledding down a hill

• A plane flying through the air

• A skateboarder going down a ramp

Multiple Choice

When does Friction Occur?

• When an object Falls

• When two objects collide

• When two objects are close by each other

• When two objects rub together