Sir Isaac Newton

• he formulated the three (3) Laws of Motion

• Newton’s Laws of Motion

Laws of Motion

1. Newton’s First Law of Motion (Law of Inertia):

• Key Concept: Objects at rest stay at rest, and objects in motion stay in
motion, unless acted upon by an unbalanced external force.
• The real-world example of a passenger in a car moving forward during a
sudden stop is a great way to demonstrate this concept in a relatable way
for students.
• Inertia -It is an inherent property of an object to resist change; mass
dependent
• Massive objects = Greater Inertia
• Smaller objects = Lesser Inertia

This law helps in understanding why objects move as they do, a fundamental idea
when analyzing forces in motion for experiments or practical challenges.

2. Newton’s Second Law of Motion (Law of Acceleration):

• Key Concept: The acceleration of an object is directly proportional to the net

force acting on it and inversely proportional to its mass.
• Greater mass = Greater amount of force is needed to accelerate

• The formula F = ma is simplified in this lesson, allowing us to easily calculate

force, mass, and acceleration in various ways.
• F=ma; m=F/a; a=F/m;

Unit:

• a = acceleration (m/s2)
• m = mass (Kg)
• F = force (N)
A NET FORCE is the total force acting on an object when all individual forces are
combined. It determines the object's acceleration, direction, and motion according to
Newton's Second Law of Motion.

Example:

Imagine a sled on a flat surface. If two people push on the sled—one pushes with 10 N
to the right, and the other pushes with 5 N to the left—the net force is the difference
between these forces, taking into account their directions:

10 N (right) - 5 N (left) = 5 N to the right.

This net force of 5 N to the right will cause the sled to accelerate to the right.

3. Newton’s Third Law of Motion (Action and Reaction):

• Key Concept: For every action, there is an equal and opposite reaction.

• The rocket-launch analogy is particularly effective for demonstrating how this

law applies to the propulsion systems that power vehicles, rockets, and even the
motion of animals.

Understanding how action-reaction forces work can aid in events where teams build
or design objects that rely on propulsion or force balance, like catapults or
hovercrafts.

Dyne
unit of force in the centimetre-gram-second system of physical units, equal to the
force that would give a free mass of one gram an acceleration of
one centimeter per second.
• One dyne equals 0.00001 Newton
• 1 Newton = 100,000 dynes
Types of Forces:

1. Gravitational Force:
o Description: This is the force of attraction between two objects due to their
mass. The Earth’s gravity pulls everything toward its center, which is why
we stay grounded.
o Example: When you drop a ball, gravity pulls it down to the ground.

2. Frictional Force:
o Description: Friction is a force that resists the motion of an object sliding or
rolling across a surface. It acts in the opposite direction of motion.
o Example: Rubbing your hands together creates heat due to friction.
Similarly, when you try to slide a book on a table, friction slows it down

3. Normal Force:
o Description: This is the supportive force exerted by a surface that is
perpendicular (normal) to the object resting on it.
o Example: When a book is lying on a table, the table exerts an upward
normal force equal in size but opposite in direction to the book's weight.
o It’s important for understanding how forces balance out. Without the
normal force, objects wouldn’t stay in place, and they would fall through
surfaces.
4. Applied Force:
o Description: An applied force is a force that is applied to an object by a
person or another object.
o Example: Pushing a shopping cart or pulling a sled. The force you apply is
an external force that makes the object move.
o This is the force you can control directly in everyday life situations, and it’s
key to many practical activities in experiments and competitions.
5. Tension Force:
o Description: This is the force transmitted through a string, rope, cable, or
any type of flexible connector.
o Example: When you pull on a rope, the tension force is created along the
rope. The same happens when you pull a kite string.
o Tension is important for understanding forces in structures like bridges or
towers, or in mechanical systems like pulleys.
6. Spring Force:
o Description: This is the force exerted by a compressed or stretched spring.
It tries to return to its equilibrium position.
o Example: When you press on a spring, it pushes back. Similarly, pulling a
slinky creates
o This force is important in understanding mechanical systems like shock
absorbers, or even in measuring forces with spring scales.
 o
7. Air Resistance (Drag):
o Description: Air resistance is a type of frictional force that acts on objects
moving through the air. It opposes the motion and depends on the shape
and speed of the object.
o Example: When you ride a bike, the wind pushes against you. Similarly, a
parachute slows you down due to air resistance.
o Air resistance is crucial for understanding how objects like planes or cars
move, as well as for experimenting with different shapes and speeds in
science projects.