Newton's Laws of Motion Notes

Recap

Free-fall Motion: The motion of an object falling free from all restraints.
Elapsed Time: The time that has passed since the falling motion began.
Acceleration Due to Gravity: $9.8 m/s^2$
Dropping Motion: Velocity is increasing.
Object Thrown Upward: Velocity is decreasing.

Newton's Laws of Motion

Lesson Objectives

Explain Newton’s laws of motion.
Differentiate mass from weight and understand how force affects the acceleration of a moving object.
Apply Newton’s laws of motion in real-life scenarios.

Sir Isaac Newton

Born on Christmas Day in 1642, three months premature.
His mother remarried a wealthy clergyman who didn’t want a stepson when Newton was 3 years old.
At age 12, Newton was enrolled in a school in Grantham, where he was bullied.
At age 15, he was ordered to quit school by his mother to be a farmer.
In 1665, due to the bubonic plague, Cambridge University closed, and Newton returned home.
He saw an apple fall from a tree, inspiring him to study gravity.
At 26, he was appointed the Lucasian professor of mathematics at Cambridge.
As an adult, Newton immersed himself in his work, had no hobbies, and never married.
He died at age 84 in March 1727.

Newton's Scientific Breakthroughs

Light
Alchemy
Calculus

Newton's Greatest Contribution

Laws of Motion.

1st Law of Motion: Law of Inertia

Aristotle on Motion: "For an object to keep moving, there should be a continuous push or pull force."
Galileo on Motion: "In the absence of opposing force (friction), a moving object will move continuously (inertia)."
Newton on Motion: "Galileo is right! AHA! My first law of Motion!"
Law of Inertia: “An object at rest remains at rest, and an object in motion remains in motion at constant speed unless acted upon by an unbalanced force.”
Inertia is the natural tendency of an object to resist changes in its state of motion.
All objects have inertia.
The more mass an object has, the more inertia it has (the harder it is to change its motion).
Forces are balanced when the net force is zero.
Forces are unbalanced when the net force is not zero.

Key Points

An object will “keep doing what it was doing” unless acted on by an unbalanced force.
It takes force to change the motion of an object.

Real-life Examples:

When a fan is turned off, the blades continue spinning due to inertia.
In a car crash, a body continues moving forward without a seatbelt.
Feeling pushed backward when a train starts moving.

Think Quick!

If the forces are balanced the resulting acceleration is zero.
Unbalanced force is required to cause acceleration.
If you push a cart pulled to the right with $5N$ of force and a friend pushing the cart to the left with $5N$ of force, the net force is zero.

2nd Law of Motion: Law of Acceleration

“The acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object.”
Newton's second law of motion pertains to the behavior of objects for which all existing forces are NOT balanced.
The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object.
Mass: The quantity of matter in an object. Used to measure how much inertia a moving object has.
Weight: The force upon an object due to gravity.
Force is calculated to be the product of objects mass and its acceleration.
Since weight is a force, it can be calculated using: $F=ma$ where:
- $F$ = force
- $m$ = mass
- $a$ = acceleration due to gravity ( $9.8 m/s^2$ )
Balanced forces cause no acceleration.
Unbalanced forces cause acceleration.
Acceleration is directly proportional to net Force and inversely proportional to Mass.
- If force increases, acceleration will increase.
- If mass increases, acceleration will decrease.

Real-life Examples:

Pushing a toy car (less mass) is easier than pushing a real car (more mass).
A stronger kick (more force) makes the ball accelerate faster.
A heavier dumbbell requires more force to lift than a lighter one.

Think Quick!

If you double the net force on an object, the acceleration doubles.
A Bicycle has a mass of $569 kg$ , if it accelerates at $4.65m/s^2$ what is the net force on the car?

Complete the Following:

Mass (kg)	Acceleration (m/s²)	Net Force (N)
4.0	4.0	16
53	3.43	172.44
25.0	4.998	1225
3	4.665	13.995

3rd Law of Motion: Law of Action and Reaction

"For every action, there is an equal and opposite reaction"
Force is a push or a pull upon an object.
According to Newton’s Third Law, whenever objects interact with each other they exert forces upon each other.
These two forces the objects exert on each other are called action and reaction forces.
They are equal in strength and opposite in direction.
They occur at the same time (simultaneously).
Right now, gravity is pulling you down in your seat, but your seat is pushing up against you with equal force. This is why you are not moving.
There is a balanced force acting on you.

Real-life Examples:

A ball bounces upward because the ground exerts an equal and opposite force back on it.
A fish swims forward because its fins push water backward (action), and the water pushes the fins forward (reaction).
When a gun is fired, the action force pushes the bullet out, and the reaction force pushes the gun backward.

Think Quick!

Forces come in pairs called action and reaction pairs.
If Manuel weighs $375 N$ and is holding a box, the floor is exerting $375 N$ of force on him.
While driving down the road, a firefly strikes the windshield of a bus and makes a mess in front of the face of the driver. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater? The forces are the same.

Summary of Newton's Laws

Newton's First Law
- Known as the Law of Inertia.
- Objects at rest stay at rest and moving objects stay in motion.
- Unless acted on by an unbalanced force.
Newton's Second Law
- Expressed as F=ma.
- More force means more acceleration.
- More mass means less acceleration.
Newton's Third Law
- Known as the Law of Action and Reaction
- If an object exerts a force on another object.
- The 2nd object exerts an equal and opposite force on the 1st.

Assignment

Answer the problem using the GRESA Method.
- Fyang, whose mass is $52 kg$ , experienced a net force of $1678.22 N$ at the bottom of a roller coaster loop. Determine Fyang’s acceleration.

Lesson 14: Newton’s Laws of Motion

Objectives:

Explain Newton’s laws of motion
Differentiate Newton’s law of motion and Galileo’s assertion on horizontal motion
Differentiate mass from weight
Apply Newton’s laws of motion in real life scenarios.

PETA #3: Rube Goldberg Machine

Pre-experiment:

Materials: bond paper/s, pencil, and other art material.
Task: Each group must submit a SKETCH to show and identify Newton’s Law of Motion present in the Rube Goldberg Machine they are going to make. Repetition in any part of the stationary machine body is NOT allowed.

Experiment & Post-experiment

Materials: any materials as long as NOT Flammable or could cause HARM to others.
Task: Create the machine following the blueprint created. Each group should take a video and documentation of the activity. The videos must include the students along with the sequence that would last at least 30 seconds to 1 minute.

Your machine’s GOAL is:

Group #1: Ringing of a Bell
Group #2: Popping of a Balloon
Group #3: Shooting a Marble in a Cup

APRIL SCHEDULE (Monday & Thursday Group):

APRIL 07, 2025. Submission of PETA#3 BLUEPRINT (via CANVAS)
APRIL 14, 2024. Written Work #5 (Coverage: Lesson 14 & Lesson 15)
APRIL 24, 2025. Submission of PETA#3 ACTIVITY SHEET (via Canvas)
APRIL 26, 2025. Submission of VIDEO DOCUMENTATION (via Google Drive to be sent by the Subject Teacher)

APRIL SCHEDULE (Tuesday & Friday Group):

APRIL 11, 2025. Submission of PETA#3 BLUEPRINT (via CANVAS)
APRIL 15, 2024. Written Work #5 (Coverage: Lesson 14 & Lesson 15)
APRIL 25, 2025. Submission of PETA#3 ACTIVITY SHEET (via Canvas)
APRIL 26, 2025. Submission of VIDEO DOCUMENTATION (via Google Drive to be sent by the Subject Teacher)