Force Vectors

​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)

Vectors, Equilibrium, Support Force, & Friction

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

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

• Friction

• Inertia

• Gravity

• Pressure

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 and in what direction?

• 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: 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

Multiple Choice

For an object at rest on a horizontal surface, the __________  must equal the object's weight

• 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

What Factors 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

Open Ended

Inside our bodies, our bones meet up at places called joints. Surrounding these joints is a soft liquid called synovial fluid. Based on what we talked about today, why do you think we have synovial fluid, and what do you think would happen if we did not? Write a paragraph to explain.