Force Lecture - V1

Open Ended

Discuss with your table partners, and then respond: What do you think happened to the spacecraft? Why is it moving away from the space station?

​Introduction to Forces and Motion

Standard - HS-PS2 Motion and Stability: Forces and Interactions

We are focusing on HS-PS2-1 to start off with.

• HS-PS2-1: Analyze data to support the claim that Newton's second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration.

From this, our learning intentions are:

• Understand the fundamental concepts of force, mass, and acceleration.

• We should know and understand Newton's laws of motion.

• Recognize the significance of "net force" when talking about motion.

Success Criteria - Forces

I can...

• ...define Newton’s First law of motion.

• ...identify examples of inertia and Newton’s first law of motion.

• ...compare and contrast mass and weight. 

• ...identify balanced and unbalanced forces.

• ...identify different types of forces.

• ...consider the effect of external forces on a system.

Learning Intention:

• We should know and understand Newton's laws of motion.

Success Criteria:

• I can define Newton’s First law of motion.

• I can identify examples of inertia and Newton’s first law of motion.

Open Ended

Answer any or all of the following questions: How do we identify acceleration? What are the units for it?

​Let's hear from Sir Newton!

Open Ended

Consider the last statement. "The greater the mass, the greater the force of attraction." Is this true? Do larger objects have larger forces of attraction? Do you know of any examples of this phenomena?

[Hint: Think of the sky, both day and nighttime. Think of how people move on the moon.]

• Sir Isaac Newton was a natural philosopher born nearby London on Christmas day, 1642.

• He was forced into farming by his mother, which was an occupation he loathed before he was sent back to school. 

• Eventually, Newton’s interests lead him to research the natural world. This would pave the way to breakthroughs in the field that eventually came to be known as Physics.

• Newton did actually observe an apple fall, and it did inspire him to formulate the theory of gravity that has managed to stay relevant to this day.

​

Sir Isaac Newton

• Newton came up with three laws that govern the motion of objects. Each of these laws are worth examining individually.

• Newton’s First Law of Motion

  • An object in motion will remain in motion unless acted upon by an unbalanced force.

• Newton’s First Law describes a concept that is known as inertia.

​

Newton's First Law

In this example, the car experiences a sudden stop, but the giraffe is still moving at the speed the car was moving before it was stopped.

Example #1:

When the llama spits, the spit is moving at the same speed as the car. Without an external force to stop or slow the spit, it drops right on top of its head.

Example #2:

The hamster is running on the wheel, but when he stops, the wheel does not--there is nothing to stop the wheel from moving.

Example #3:

​Inertia Examples

• Mass is a property of matter that equates to how much “stuff” makes up an object. 

• The metric unit for mass is grams.

• When you think about it, an object’s mass is directly correlated to how much it resists motion.

• If you try and move a truck loaded with objects, it would be a lot harder than trying to move the same truck, but unloaded.

Mass

• Inertia is an object’s tendency to stay in whatever state it is in.

• If an object is moving, then it will continue moving. If it’s not, it shouldn’t spontaneously begin doing so.

Inertia

A Tale of Two Terms

Learning Intention:

• We should know and understand Newton's laws of motion.

Success Criteria:

• I can define Newton’s First law of motion.

• I can identify examples of inertia and Newton’s first law of motion.

Open Ended

How would you define inertia in your own words? Talk with your table: How might this first law relate to the spacecraft getting lost in its mission?

Why is any of this important? Do we need it for later?

Learning Intention:

• We should know and understand Newton's laws of motion.

• Understand the fundamental concepts of force, mass, and acceleration.

Success Criteria:

• I can compare and contrast mass and weight. 

• I can consider the effect of external forces on a system.

Mass vs. Weight

• Chances are that when you heard the term "mass", you probably thought of "weight".

• In everyday speech, we typically use the terms interchangeably, but this is not the case.

• There is a relationship between mass and weight that will be addressed at a later time.

• Mass is a property of matter that equates to how much “stuff” makes up an object. 

• The metric unit for mass is grams.

• When you think about it, an object’s mass is directly correlated to how much it resists motion.

• Your mass stays the same, regardless of where in the universe you are.

Weight

• Weight is a measure of the force the Earth is pulling you down with.

• Your weight is different, depending on what is pulling you gravitationally. The Moon, for example, doesn’t pull as hard as the Earth so you weigh less on the moon than you do on Earth.

Mass

Mass and Weight: What's the difference?

• Newton’s Second Law of Motion

  • The acceleration of an object that is produced by a net force is directly proportional (If one increases, the other does too) to the magnitude (size) of that force. It will be inversely proportional (when one increases, the other decreases.) to the mass.

• This is a fancy way of saying that more mass requires more force to get an object moving.

• Simply put:

   

Newton's Second Law

• ​Force and Weight are the same term. The difference is weight deals with acceleration due to gravity.

• ​When an object falls with no forces acting on it other than gravity, it is in freefall.

• An object's acceleration in freefall on Earth is:

  • 9.8 m/s²

  • 32 ft/s²

• If an object fell on another planet, it would have a constant acceleration determined by the mass of the planet.

Freefallin'

Math Response

Bob has a mass of 70 kg. If he is standing on Earth, which accelerates him downward at a rate of roughly 10 m/s², what would his weight be?

$$Force\ \left(Weight\right)=\ Mass\ \cdot\ Acceleration$$

Type answer here

Correct Answer: 700

Deg^°

Rad

Math Response

Bob has a mass of 70 kg. If he is standing on the Moon, which accelerates him downward at a rate of roughly 2 m/s², what would his weight be?

$$Force\ \left(Weight\right)=\ Mass\ \cdot\ Acceleration$$

Type answer here

Correct Answer: 140

Deg^°

Rad

Math Response

Bob weighs 140 N on the moon, which accelerates him downward at a rate of roughly 2 m/s², what would his mass be?

$$Mass=\ \frac{Force}{Acceleration}$$

Type answer here

Correct Answer: 70

Deg^°

Rad

Math Response

Timmy woke up and found himself on another planet! He quickly pulls out his pocket scale and weighs himself. He finds his weight to be 900N. If his mass is 80kg, what is the acceleration due to gravity on this mysterious planet?

$$Acceleration=\ \frac{Force}{Mass}$$

Type answer here

Correct Answer: 11.25

Deg^°

Rad

Learning Intention:

• We should know and understand Newton's laws of motion.

• Recognize the significance of "net force" when talking about motion.

Success Criteria:

• I can identify balanced and unbalanced forces.

• I can identify different types of forces.

• I can consider the effect of external forces on a system.

​Newton’s Third Law of Motion states, “For every force applied, there is an equal and opposite reactionary force.”

• So any time a force is applied, there is some equal and opposite force.

Newton's Third Law

• So, when we talk about Newton’s third law, there’s an important distinction. 

• Newton’s third law specifically affects two different objects acting on one another.

• Some examples are:

Newton's Third Law

Action-Reaction Pairs

​Action Force	​Reaction Force
​Foot pushes on ground	Ground pushes​ foot forward
​You push on wall	Wall pushes back on you​
​Tire pushes backwards on ground	Ground pushes car forward​
​Your weight pushes down on Earth	Earth pushes back up on you​

Open Ended

Final Question! How might Newton's Third Law explain the loss of the spacecraft?

Standard - HS-PS2 Motion and Stability: Forces and Interactions

We are focusing on HS-PS2-1 to start off with.

• HS-PS2-1: Analyze data to support the claim that Newton's second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration.

From this, our learning intentions are:

• Understand the fundamental concepts of force, mass, and acceleration.

• We should know and understand Newton's laws of motion.

• Recognize the significance of "net force" when talking about motion.

Success Criteria - Forces

I can...

• ...define Newton’s First law of motion.

• ...identify examples of inertia and Newton’s first law of motion.

• ...compare and contrast mass and weight. 

• ...identify balanced and unbalanced forces.

• ...identify different types of forces.

• ...consider the effect of external forces on a system.

Building Bridges

Conceptual Physics - Project #1

• You are building a bridge.

• The goal is to have your bridge...

  • Have four walls, it should be able to stand by itself.

  • Holds 25lbs or more.

  • Is built out of popsicle sticks and white glue.

• Requirements:

  • Bridge should span a 28cm gap (meaning it should be > 28cm long)

  • Bridge should be 8cm wide.

​

What's the deal?

• This will tell you everything we're looking for for grading purposes.

• Participation scores will be awarded based on group member reviews.

​

How am I graded?

• The start of any good engineering project is research!

• The first step is to research other bridges to get ideas.

• Following that, you will complete a blueprint.

• There's a google form that we will start tomorrow!

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Where do I start?