Force and Laws of Motion: Physics Explained
In the
world of physics, force and the laws of motion are
key. They help us understand the physical universe. This article will explain
these important ideas. It will show how force and motion affect
objects around us.
An object
being pushed across a table by an unseen force, with arrows indicating the
direction and magnitude of the force. Another arrow shows the equal and
opposite force of friction pushing back against the object. In the background,
a diagram shows the three laws of motion with corresponding illustrations.
5.
THE
FUNDAMENTAL UNIT OF LIFE
6.
TISSUES
7.
MOTION
9.
GRAVITATION
10.
WORK
AND ENERGY
11.
SOUND
12.
IMPROVEMENT
IN FOOD RESOURCES
Key Takeaways
Ø
Explore
the definition and types of force, including friction
force and gravitational force.
Ø
Understand
the three laws of motion proposed by Sir Isaac Newton, which govern
how objects move.
Ø
Learn
about the relationship between force, mass, and acceleration, as described by
Newton's second law.
Ø
Discover
how the SI unit of force, Newton, is used to measure the strength of a
force.
Examine
the concept of momentum and its conservation, a fundamental principle in the
study of motion.
Understanding the Fundamentals
of Force
Physics is
all about force, a key idea that helps us understand how things move and
behave. But what is force, really? And how does it show up in our world?
Let's dive into what force means and the various forces that shape our daily
lives.
What is Force?
Force is
the push or pull between two objects that can change their speed, direction, or
shape. It's measured in newtons (N) and is a vector, meaning it has size and
direction. Force is key to how objects move and how energy moves from one to
another.
Types of Forces
There are
many forces in the world, each with its own way of working. Here are some
common ones:
Friction Force: This force stops objects from moving
past each other easily. It can help or slow things down, depending on the
situation.
Gravitational Force: This force pulls objects with mass
towards each other, like the Earth and things on it. It makes things fall and
keeps planets in orbit.
Momentum: This is how hard it is to stop an
object from moving. It's the product of an object's mass and speed. Forces can
change an object's momentum.
Knowing
about these forces helps us understand how things move and behave.
Create an
image showcasing the different types of forces in physics, depicting them as
distinct and recognizable physical phenomena. Use a mix of colors and shapes to
convey the nature of each force, whether it be gravitational,
electromagnetic, centripetal,
or frictional. Make sure to include enough
detail and variety to convey the full range of forces that exist in the world
around us.
Force |
Description |
Example |
|
Friction
Force |
Opposes
the relative motion between two surfaces in contact |
The
resistance felt when pushing a box across a floor |
|
Gravitational
Force |
Attractive
force between objects with mass |
The
force that causes objects to fall towards the Earth |
|
Momentum |
Measure
of an object's resistance to changes in motion |
The
force required to stop a moving car |
The Laws of Motion
Sir Isaac
Newton introduced the fundamental laws of motion. These three laws help us
understand the physical world. They tell us how objects move and the forces
that affect them. Let's explore each law and see why they're important.
The First Law of Motion
The first
law, or the law of inertia, says that objects stay still or keep moving unless
a force stops them. This means objects don't like to change how they're moving.
This is because of something called inertia.
The Second Law of Motion
The second
law links force, mass, and speed. It says how fast an object speeds up
depends on the force on it and its mass. The formula F = ma shows this, where F is force, m is mass, and a is speed.
The Third Law of Motion
The third
law, or the action-reaction law, says every action has an equal opposite
reaction. When one object pushes or pulls another, the second object does the
same back. This helps us understand forces in different situations.
The Newton (N) is the SI unit
for force, named after
Sir Isaac Newton. Knowing these laws helps us understand how objects move and
the forces that act on them.
An object
at rest and an equal force acting on it causes it to move. Another object in
motion is being pushed by a greater force in the opposite direction, causing it to
slow down and eventually stop. An image shows a person pushing two identical
boxes of different weights, with one moving faster than the other due to a
stronger push.
"Understanding
the laws of motion is the key to unlocking the mysteries of the universe."
- Sir Isaac Newton
Conclusion
In this
article, we've looked into the basics of force and the laws of motion. These
are key to understanding physics. We learned about the nature of force and
Newton's three laws of motion. This gives us a deep look into how the world works.
As we end
our exploration of physics, it's clear that studying force and motion is vital.
It's not just for school. It helps us understand the world better. By getting
these ideas, we open doors to new discoveries and innovations. These will keep
pushing what we can do and know.
FAQ
What is the force in physics?
Force is a
vector that shows how two objects interact. It's the push or pull that changes
an object's speed, shape, or direction.
Forces in
physics include: - Friction force:
This is the force that stops two surfaces from moving past each other. - Gravitational force: This pulls objects with
mass together, like the Earth and an object. - Momentum:
This is how much motion an object has found by multiplying its mass and speed.
The first law says
that objects stay still or keep moving at the same speed unless a force acts on
them.
The second law links
force and acceleration. The more force on an object, the more it will speed up.
But, the heavier the object, the less it will speed up.
The third law says
that every action has an equal and opposite reaction. When one object pushes or
pulls another, the second object does the same back.
The Newton
(N) is the SI unit for force. It's the force needed to make a one-kilogram
object speed up by one meter per second squared.
===============
NCERT Solutions for Class 9 Science
Chapter 9 Force and Laws of Motion
NCERT Solutions
Class 9 Science Chapter 9 Force and Laws of Motion –
Looking
for Class 9 Science NCERT solutions for Chapter 9 on Force and Laws of Motion?
You'll find all the answers, explanations, and images in one place. If you're
using NCERT textbooks to study Science, these solutions will help you
understand the chapter better. Don't forget to check out the Class 9 notes on
Chapter 9 for a complete grasp of Force and Laws of Motion.
NCERT Solutions for Class 9 Science Chapter 9 Force and Laws of Motion
ü
Topics
and Sub Topics in Class 9 Science Chapter 9 Force and Laws of Motion:
ü
Force
and Laws of Motion
ü
Balanced
and Unbalanced Forces
ü
First
Law of Motion
ü
Inertia
and Mass
ü
Second
Law of Motion
ü
Third
Law of Motion
ü
Conservation
of Momentum
Here we
have given Class 9 NCERT Science Textbook Solutions for Chapter 9 Force and
Laws of Motion.
Question
1. Which of the following has more inertia:
(a) a rubber ball and a stone of the same size?
(b) a bicycle and a train?
(c) a five-rupee coin and a one-rupee coin?
Answer:
(a) A stone of the same size
(b) a train
(c) a five-rupees coin
As the mass of an object is a measure of its inertia, objects with more mass
have more inertia.
More Resources for CBSE
Class 9
Question 2. In the following example, try to identify
the number of times the velocity of the ball changes.
“A football player kicks a football to another player of his team who kicks
the football towards the goal The goalkeeper of the opposite team collects the
football and kicks it towards a player of his own team”.
Also, identify the agent supplying the force in each
case.
Answer:
In the given scenario, the velocity of the football changes four(4) times:
- First Kick: When the first player kicks the football to another
player.
- Second Kick: When
the second player kicks the football towards the goal.
- Goalkeeper’s Collection: When the goalkeeper collects the football.
- Goalkeeper’s Kick: When
the goalkeeper kicks the football towards a player of his own team.
Agents supplying the force:
- First Kick: First
player.
- Second Kick: Second
player.
- Goalkeeper’s Collection: Goalkeeper.
- Goalkeeper’s Kick: Goalkeeper.
The velocity of football changed four times.
Question 3. Explain why some of the leaves may get
detached from a tree if we vigorously shake its branch.
Answer:
When the tree’s branch is shaken vigorously the branch
attains motion but the leaves stay at rest. Due to the inertia of rest, the
leaves tend to remain in their position and hence detach from the tree to fall
down.
Question 4. Why do you fall in the forward direction
when a moving bus breaks to a stop and fall backward when it accelerates from
rest?
Answer:
When a moving bus brakes to a stop: When the bus is
moving, our body is also in motion, but due to sudden brakes, the lower part of
our body comes to rest as soon as the bus stops. But the upper part of our body
continues to be in motion and hence we fall in a forward direction due to the inertia
of motion.
When the bus accelerates from rest we fall backward: When the bus’ is stationary
our body is at rest but when the bus accelerates, the lower part of our body
being in contact with the floor of the bus comes in motion, but the upper part
of our body remains at rest due to inertia of rest. Hence we fall in the backward
direction.
Class 9 Science NCERT
Textbook – Page 126-127
Question 1. If action is always equal to the reaction, explain how a horse
can put a cart?
Answer:
The third law of motion states that action is always
equal to the reaction but they act on two different bodies.
In this case, the horse exerts a force on the ground with its feet while
walking, the ground exerts an equal and opposite force on the feet of the
horse, which enables the horse to move forward and the cart is pulled by the
horse.
Question 2. Explain, why is it difficult for a fireman
to hold a hose, which ejects a large amount of water at a high velocity.
Answer:
The water that is ejected out from the hose in the
forward direction comes out with a large momentum and an equal amount of momentum
is developed in the hose in the opposite direction hence the hose is pushed
backward. It becomes difficult for a fireman to hold a hose that experiences
this large momentum.
Question 3. From a rifle of mass 4 kg, a bullet of mass 50 g is fired
with an initial velocity of 35 m/s. Calculate the initial recoil velocity of
the rifle.
Answer:
(m1) Mass of the rifle = 4 kg
(m1) Mass of the bullet = 50 gms = 0.5 kg
(v2) Velocity of the bullet = 35 m/s
(v1) Recoil Velocity of the rifle =?
According to the law of the conservation of momentum
The momentum of rifle = momentum of the bullet
M1v1 = m2v2
4 kg x v1 = 0.5 kg x 35 m/s
V1 =0.05 kg x 35 m/s / 4 kg
= 1.75/4
= 0.4375 m/s
The recoil velocity of the rifle =
0.4375 m/s
Question 4. Two objects of masses 100 g and 200 g are
moving along the same line and direction with velocities of 2 m/s and 1 m/s
respectively.
They collide and after the collision, the first object moves at a velocity of
1.67 m./s. Determine the velocity of the second object.
Answer:
M1 = 100 g = 0.1 kg
M2 = 200 g = 0.2 kg
U1 = 2 m/s
U2 = 1 m/s
After collision :
V1 = 1.67 m/s
V2 = ?
M1u1 + m2u2 = m1v1 +m2v2
(0,1 kgx2) + (0.2 kg x1) = (0.1 kg x 1.67) + (0.2 kg x v2)
0.2 + 0.2 = 0.167 + 0.2v2
V2= (0.4 - 0.167)/0.2
=0.233/0.2 = 1.165 m/s
\The
velocity of the second object is 1.165 m/s
*** See You Again ***
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