M4 1stSem Final Chapter III (Law of Motion)

Laws of Motion

Changes in Motion

Objective:​

Describe how force affects the motion of an object.

​In physics, motion is the phenomenon of an object changing its position over time relative to a reference point.

​Changes in Motion

​Forces do not cause MOTION. A force is an action exerted on an object that may change the object's state of rest or motion.

​

Forces can cause acceleration.​

​The SI unit of force is the Newton (N).

​

1 N = 1 kg . m/s²​

​

Weight is a force.​

Weight = mass . gravity​

Multiple Choice

Force is _________.

• an action exerted on an object that may change the object's state of rest or motion.

• an action exerted on an object that may change the object's state of moving.

• an acceleration exerted on an object that may change the object's state of rest or motion.

Multiple Choice

Forces can cause ________________.

• a change in direction

• acceleration

• acceleration and/or a change in direction

​Types of Forces

​

Contact forces result from physical contact between two objects. Examples: friction, a push or pull, an applied force.​

​

Field forces do not involve physical contact between two objects. Examples: gravity, magnetic force, an electric field.​

​Two types of Applied Force

Multiple Choice

Friction is a type of _______________.

• Contact Force

• Field Force

Multiple Choice

Gravity is a type of __________________.

• Contact Force

• Field Force

Multiple Choice

What type of force is shown ?

• Contact Force

• Field Force

Multiple Choice

What type of force is shown ?

• Contact Force

• Field Force

Multiple Choice

What type of force is shown ?

• Contact Force

• Field Force

Multiple Choice

What type of force is shown ?

• Contact Force

• Field Force

Multiple Choice

What type of force is shown ?

• Contact Force

• Field Force

​Force Diagrams

​Force is a vector and has magnitude and direction.

​

A free-body diagram helps analyze a situation​.

Forces on the y-axis are independent of the forces on the x-axis.​

Multiple Choice

Force diagrams allow us to identify __________________.

• forces acting on an object

• masses of objects

• acceleration

​Activity

Rubber bond​https://www.youtube.com/shorts/Sc-X_3PWE-U

Balloon rubbed
https://www.youtube.com/watch?v=QzprKH1bLJM

Book Falling from a table
https://www.youtube.com/shorts/IYzwTy43sGQ

​Newton's First Laws of Motion

Objectives:​

• Explain the relationship between the motion of an object and the net external force acting on the object.

• Determine the net external force on an object.

• Calculate the force required to bring an object into equilibrium.

​Newton's First Law (Inertia)

​

• An object at rest will stay at rest, and an object in motion will stay in motion with the same velocity (speed and direction), unless acted upon by an unbalanced external force.

​Newton's First Law

Multiple Choice

Which following is the first law of motion?

• An object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force.

• The force acting on an object is equal to the mass of that object times its acceleration

• For every action there is an equal an opposite reaction.

Multiple Choice

What causes objects to move or stop moving?

• a force

• inertia

• Newton's first law

Multiple Choice

If all forces acting on a object are equal, are the forces ...

• balanced

• unbalanced

Multiple Choice

If the net force of an object is greater than zero, will the object move?

• yes

• no

Inertia

​Inertia is the tendency of an object to resist being moved or, if the object is moving , to resist a change in speed or direction.

​Mass is a measure of inertia. The inertia of an object is proportional to the mass of an object. The greater the mass, the greater the inertia.

Multiple Choice

Inertia is the tendency of a motionless object to _______________.

• remain motionless

• accelerate

• start moving

Multiple Choice

When mass decreases, inertia

• decrease

• increases

• remains the same

Multiple Choice

When mass increases, inertia

• decrease

• increases

• remains the same

Multiple Choice

Which would be harder to move?

• a pencil

• an elephant

Multiple Choice

Which object has more inertia?

• a pencil

• an elephant

Multiple Choice

If you kicked a ball in space, will it eventually slow down and come to a stop?

• no it can go on forever

• yes air resistance will slow it down

Open Ended

Scenario…

You are riding a bus to school. You stand up to walk to the front of the bus to ask your friend a question.

SUDDENLY, something runs in front of the bus and the bus driver slams on his brakes …….

What will happen to you and why?

​The sum of forces acting on an object is the net force.

​

Net force is a single force whose external effects on a rigid body are the same as the effects of several actual forces acting on the body.​

Multiple Choice

What is the net force on the airplane?

• 700 N to the right

• 100 N to the left

• 800 N to the right

• 900 N to the right

Multiple Choice

What is the net force on the box?

• 50 N to the right

• 30 N to the right

• 80 N to the right

• 80 N to the left

​Write your answers in your notebook.

​1. What does Newton's First Law of motion states?

2. A ______is an action exerted on an object that may change the object's state of rest or motion.

3. The inertia of an object is _______ to the mass of an object.

​4.

​5.

​Compute the Net Forces in each diagram.

​Newton’s Second and Third Laws of Motion

​Objectives:

• ​Describe an object’s acceleration in terms of its mass and the net force acting on it.

• Predict the direction and magnitude of the acceleration caused by a known net force.

• Identify action-reaction pairs.

​Newton's Second Law of Motion

​Objects that are either at rest or moving with constant velocity are said to be in equilibrium.

​

Equilibrium is the state in which the net force on an object is zero.​

Multiple Choice

Which object is in equilibrium?

​Newton's Second Law -- the acceleration of an object is directly proportional to the net force acting on an object and inversely proportional to the object's mass.

​According to Newton's second law, if equal forces are applied to two objects of different masses, the object with the greater mass will experience a smaller acceleration, and the object with less mass will experience a greater acceleration.

​F = ma

Force is in Newtons (N)

Mass is in kilograms (kg)

Acceleration is in m/s²​

​Roberto and Laura are studying across from each other at a wide table. Laura slides a 2.2 kg book toward Roberto. If the net force acting on the book is 1.6 N to the right, what is the book’s acceleration?

Multiple Choice

This law states that if two objects interact, the magnitude of the force exerted on object 1 by object 2 is equal to the magnitude of the force simultaneously exerted on object 2 by object 1, and these two forces are opposite in direction.

• Newton's First Law of Motion

• Newton's Second Law of Motion

• Newton's Third Law of Motion

• Equilibrium

Multiple Choice

________ is the state in which the net force on an object is zero.​

• Newton's First Law of Motion

• Newton's Second Law of Motion

• Newton's Third Law of Motion

• Equilibrium

Multiple Choice

If a force of 20 N is applied to an object with a mass of 5 kg, what will its acceleration be? (Ignore friction)

• 20 m/s²

• 100 m/s²

• 4 m/s²

• 15 m/s²

​Newton's Third Law -- if two objects interact, the magnitude of the force exerted on object 1 by object 2 is equal to the magnitude of the force simultaneously exerted on object 2 by object 1, and these two forces are opposite in direction.

​Forces always exist in pairs.

​

The book exerts a force on the table, the table exerts a force on the book.​

Action: The rocket engine pushes hot gases downward at high speed.

Reaction: The gases push the rocket upward with an equal and opposite force, causing it to lift off.

​The rocket pushes gases down, and the gases push the rocket upward.

Action: As you jump forward into the water you push the boat backward.

Reaction: The boat pushes you forward with an equal and opposite force, allowing you to move into the water.

boat moves backward when you jump off.

Action: The bird pushes air downward with its wings.
Reaction: The air pushes the bird upward with an equal and opposite force.

This upward reaction force is what helps the bird lift off and stay in the air.

Action: The hammer exerts a force on the nail, driving it into the wood.

Reaction: The nail exerts an equal and opposite force back on the hammer.

You feel resistance or a “jolt” in your hand when you hit a nail — the nail is pushing back on the hammer with the same amount of force..

Action: The swimmer’s hands and feet push the water backward.

Reaction: The water pushes the swimmer’s body forward with an equal and opposite force.

That forward reaction force is what allows the swimmer to move through the water.

Action: You apply a force on the wall by pushing it(forward).

Reaction: The wall applies an equal and opposite force back on you(backward).

You feel pressure or resistance on your hand, even though the wall doesn’t move.

Action: When the gunpowder explodes, it pushes the bullet forward at high speed out of the barrel.

Reaction: The bullet pushes back on the gun with an equal and opposite force, causing the gun to move backward (recoil).

That backward motion of the gun is the recoil, and it clearly shows the action–reaction force pair.

Multiple Choice

________ is the state in which the net force on an object is zero.​

• Newton's First Law of Motion

• Newton's Second Law of Motion

• Newton's Third Law of Motion

• Equilibrium

Multiple Choice

________ is the state in which the net force on an object is zero.​

• Newton's First Law of Motion

• Newton's Second Law of Motion

• Newton's Third Law of Motion

• Equilibrium

Multiple Choice

​Forces always exist in __________.

• Newton's First Law of Motion

• motion

• pairs

• Equilibrium

Multiple Choice

Identify the force action-reaction pairs for a bat and a ball.

• The ball hits the bat, the bat hits the ball.

• The bat hits the ball, the ball flies to the outfield.

• The batter swings the bat, the bat hits the ball.

• The bat hits the ball, the ball changes direction.