What is Force? - Part 1| Forces and Motion | Physics | Infinity Learn NEET

Summary

This script delves into the concept of force, clarifying misconceptions and explaining its true nature. It challenges the simple idea of force as just a push or pull, illustrating how forces like gravity and friction affect motion. The discussion reveals that objects can be subject to forces without moving, and that motion continues unless acted upon by an external force. It concludes by emphasizing that force is an interaction resulting in acceleration, not just movement.

Takeaways

• 📚 Force is not just a push or pull; it's a result of interaction with another object.
• 🔄 Even stationary objects experience forces, like the gravitational force pulling down and the normal force from the ground pushing up.
• 🧭 A net force of zero means no change in the object's state, whether at rest or in uniform motion.
• 💥 An unbalanced force results in a change in the object's motion, such as starting, stopping, or changing direction.
• 🛑 Friction is a force that opposes motion and can eventually stop an object.
• 🌌 In a frictionless environment with no air resistance, an object in motion will continue moving at a constant velocity.
• 🏃‍♂️ When an external force is applied to a moving object, it can cause acceleration, changing the object's velocity.
• 🔄 Forces always occur in pairs due to Newton's third law of motion (action and reaction forces).
• 🌟 Understanding force involves observing the effects on objects rather than seeing or touching it directly.
• 🔮 Further concepts about force will be explored in subsequent educational content.

Q & A

What is the initial definition of force that textbooks often provide?

The initial definition provided by textbooks is that force is a push or pull upon an object.

Why does the textbook definition of force not fully explain the concept?

The textbook definition does not fully explain the concept because it only considers the action of humans pushing or pulling an object, and it does not account for forces acting on stationary objects or the balance of forces.

What forces act on a stationary ball at rest on the ground?

A stationary ball at rest on the ground experiences gravitational force pulling it towards the Earth and a normal force from the ground acting in the opposite direction.

Why does the net force on the stationary ball equal zero?

The net force on the stationary ball equals zero because the gravitational force and the normal force are equal in magnitude and opposite in direction, thus balancing each other out.

What happens when a person softly kicks the ball?

When a person softly kicks the ball, the forces are no longer balanced, resulting in a net force that causes the ball to move and change its position.

What force causes the ball to stop after it has been kicked?

Friction is the force that eventually stops the ball after it has been kicked, as it acts in the opposite direction to the motion of the ball.

In a frictionless environment, will a moving ball ever stop on its own?

In a frictionless environment, a moving ball will not stop on its own; it will continue to move at a uniform velocity unless acted upon by an external force.

What is the relationship between net force and an object's motion?

If the net force on an object is zero, a stationary object will remain at rest, and a moving object will continue to move at a uniform velocity.

What happens when an external force is applied to a moving ball at a uniform velocity?

When an external force is applied to a moving ball at a uniform velocity, the ball will accelerate, and its velocity will change.

How does force relate to the interaction between objects?

Force is a result of the interaction between objects; when you kick a ball, your leg exerts a force on the ball, and the ball exerts an equal and opposite force on your leg.

What is the significance of understanding force in terms of an object's motion?

Understanding force in terms of an object's motion is significant because it helps us predict how objects will react when forces are applied to them, whether they are at rest or in motion.

Outlines

00:00

📚 Understanding Force

The paragraph begins by questioning the textbook definition of force as a push or pull, suggesting it is inadequate. It challenges the reader to consider forces acting on a stationary ball on the ground, revealing that there are indeed forces at play, such as gravity pulling the ball towards the Earth and the normal force from the ground balancing it out. The concept of net force is introduced, explaining that for an object to move, there must be an unbalanced force. The example of a kicked ball illustrates the application of an unbalanced force leading to motion. The paragraph further discusses how friction eventually stops the ball, and uses a thought experiment to demonstrate that in the absence of external forces like friction, an object in motion will continue moving at a constant velocity. The key takeaway is that force is not just about causing motion but also about interactions between objects, and that an object will maintain its state (at rest or in uniform motion) unless acted upon by a net external force.

Keywords

💡Force

Force is described as a push or pull upon an object resulting from its interaction with another object. It's a fundamental concept in physics that can change the motion of an object. In the script, force is exemplified by a person kicking a ball, causing it to move. The concept is further illustrated by explaining that even stationary objects are subject to forces, such as the gravitational force pulling a ball towards the Earth and the normal force exerted by the ground.

💡Gravitational Force

Gravitational force is the attractive force that exists between any two bodies with mass, such as the Earth and the ball in the script. It's what pulls the ball towards the center of the Earth. This force is balanced by the normal force when the ball is at rest, resulting in no net force and no movement.

💡Normal Force

The normal force is the force exerted by a surface that supports the weight of an object resting on it. In the script, it's the force that the ground applies to the ball to counteract gravity. This force is crucial in maintaining the ball's stationary state when no other forces are acting on it.

💡Net Force

Net force refers to the vector sum of all the forces acting on an object. If the net force is zero, as in the case of the ball at rest, there is no change in the object's state (either it remains at rest or continues moving at a constant velocity). The script uses the concept to explain why the ball doesn't move until an unbalanced force, like a kick, is applied.

💡Friction

Friction is the force that resists the relative motion of two objects in contact. In the script, friction is what eventually stops the ball after it has been kicked. It acts in the opposite direction of the ball's motion, illustrating how forces can oppose each other and change an object's state of motion.

💡Displacement

Displacement is the change in position of an object. The script mentions displacement when discussing how the ball moves after being kicked, emphasizing that a change in position is a direct result of an unbalanced force being applied to the object.

💡Uniform Velocity

Uniform velocity means moving at a constant speed in a straight line. The script uses the example of a ball moving at a uniform velocity of 2m/s on a frictionless surface to explain that an object in motion will continue to move at the same speed and in the same direction unless acted upon by an external force.

💡Frame of Reference

A frame of reference is a set of criteria or a system used to describe the motion of an object. In the script, the screen is used as a frame of reference to describe the motion of the ball. This concept helps to understand how the motion of an object can be perceived differently depending on the observer's perspective.

💡Balanced Forces

Balanced forces occur when two or more forces of equal magnitude but opposite direction act on an object, resulting in no net force and no change in motion. The script explains that the gravitational force and the normal force are balanced when the ball is at rest on the ground.

💡Acceleration

Acceleration is the rate of change of velocity of an object with respect to time. The script discusses acceleration in the context of an external force being applied to the ball, causing it to change its velocity from 2m/s to 3m/s, illustrating how a net force can cause an object to speed up.

💡Interaction

Interaction, in the context of the script, refers to the mutual actions or influences between objects, such as when a person kicks a ball. The force exerted by the leg on the ball and the force exerted by the ball on the leg are examples of interactions that result in changes in motion.

Highlights

Force is often misunderstood as merely a push or pull, but it involves more complex interactions.

A stationary object can still be subject to forces, such as gravity and the normal force from the ground.

The net force on an object is zero when balanced forces act in opposite directions.

An object will not move unless there is a net force acting upon it.

The introduction of an unbalanced force can change an object's position.

Friction is a force that can oppose motion and eventually stop an object.

In a frictionless environment, an object will continue moving at a constant velocity unless acted upon by an external force.

Objects in motion do not require a net force to maintain their velocity.

An object at rest will remain at rest if no net force is applied.

An object moving at a constant velocity will continue to do so unless a net force is applied.

The application of an external force can cause an object to accelerate.

Once an external force is removed, an object will continue moving at the new velocity unless other forces act upon it.

Force is an interaction between objects, and it can be mutual, as seen when kicking a ball.

The strength of the force applied can influence the motion of an object.

There are many concepts of force that will be explored in further detail.

Force is not something that can be seen or touched, but it can be understood through its effects on objects.

Assumptions about the presence or absence of force based on an object's state of motion can be misleading.

Force is a push or pull resulting from the interaction of objects, and it can be mutual.

Transcripts

What is Force?

Let me tell you what you will probably read in your text books

Force is a push or pull upon an object right?

While this cannot be classified as incorrect,

it hardly explains anything about the concept of force

This is what you will assume after reading this definition

you will imagine a stationary object on the ground

and someone pushing it or pulling it.

Yes, when force is applied

the stationary object will move

but this does not explain the concept of force entirely.

Before we move on to the definition of force, lets clear a few

misconceptions about it.

Let me ask you a question,

this ball is lying at rest on the ground

it's stationary, not moving at all.

Is there any force acting on it?

Listen to my question carefully,

are there any forces acting on the ball

when it is stationary?

If your answer was a no, or if you didn't have an answer

it means you don't know the concept of force yet.

The answer is yes! There are forces

acting on this ball.

There is a gravitational force, which is trying to pull the ball towards

the centre of the Earth.

And the ground is applying an equal force, exactly in the

opposite direction.

This force is called the normal force

Because these two forces are balanced, they do not change the

position of an object. The net force

acting on the ball is zero.

So what does this tell you? Just humans

pushing or pulling is not the only kind of force.

And just because there are forces acting on an object

will not mean the object will move. For the

object to move, there has to be some net force.

So now let's say a person softly kicks the ball,

what happens then? Yes, the position of the

ball changes. Why did the position

change? It's because there was another magnitude

of force acting on it, and this time,

the forces were not balanced. The ball

moved, and there was displacement.

But hold on, why did the ball stop moving after

covering 15 meters? The ball started moving

at a pace, and then slowly came to a halt.

If there is no force from the other side to stop it,

how did it stop?

Was there a force which stopped it? Yes,

It was friction that stopped the ball.

While the force you applied was toward the right,

the force of the friction was toward the left.

Let's make it even more interesting,

Assume your screen to be a frame of reference for this example.

Also assume that this straight horizontal line is a

a frictionless floor, and there is no air resistance.

The ball appears from the left of your screen, and moving

towards the right at a uniform velocity

of 2m/s. The only two forces

acting on the ball are the gravitational and the normal forces

which net each other out.

In this setting, will the ball ever stop moving?

No it won't, it will continue to move along the same path

at the same speed, unless there is another

external force which acts on it. Here as the forces are balanced

the ball will continue to move at 2m/s

Most people assume that if the object is moving,

then there is some net force acting on it, and that's not true.

An object will continue to move at uniform velocity

even if the net force on it is zero.

So there are two things we've learnt here.

First, if the object is stationary, and the net force

acting on it is zero, then it will

continue to remain at rest.

Second, if the object is moving at uniform velocity,

and the net force acting on it is zero, then it will

continue to move at that same uniform velocity.

Now when this ball is moving at 2m/s

and there is an external force applied from the left, what

will happen?

Yes, the ball will accelerate. It's

velocity will change. Let's say the velocity

changes to 3m/s

after this external force is applied. After that,

the ball will continue to move at 3m/s, unless

acted upon by another external force.

So nobody's really seen or touched force

it can only be understood by knowing what happens to an

object when force is applied to it. If

the body is stationary, do not assume that there is no

force acting on it.

And if the body is in uniform

motion, do not assume that there is some net

force acting on it. So what is force?

Force is a push or a pull upon an object, resulting from its

interaction with another object.

So when you kick the ball

The ball also exerts a force onto your leg.

But as the force of your leg gets stronger

the ball moves to the right.

There are many more concepts we need to understand about force.

Which we will cover in the next video.