### Select your language

Suggested languages for you: |
|

## All-in-one learning app

• Flashcards
• NotesNotes
• ExplanationsExplanations
• Study Planner
• Textbook solutions

# Newton's First Law Save Print Edit
Newton's First Law
• Calculus • Decision Maths • Geometry • Mechanics Maths • Probability and Statistics • Pure Maths • Statistics Newton's first law of motion states that a body will stay at rest or keep moving at a constant velocity unless acted upon by an unbalanced force. The first part seems to make sense since objects at rest typically do not just start moving. However, the second part appears to contradict our everyday experiences.

When a ball is thrown, it does not keep moving forever. It eventually stops. For a car to move, for the ball to stop, or for a plane to stay in the air, a constant force must be applied. To understand Newton's first law of motion, you need to understand the forces that act on a body in motion. Demonstration of Newton's first law

## Newton's first law in everyday life

In everyday life, we (and other objects) experience resistive forces, whether they be gravity, friction, etc. These are what slow us down, requiring the application of constant force to keep moving.

Think of something like an ice skating rink, which is a surface with very little friction. If you push a hockey puck, it will glide much farther than it would on a table (where there is more friction). However, there still is some friction present in its interaction with the ice, so it eventually stops. Newton's first law proposes that if you pushed this same hockey puck on a surface completely free of fiction, it would retain the exact velocity it had when it left the stick, and it would keep gliding forever unless some other forces were to act on it.

### Inertia

Inertia is a quantity that relates to the willingness of objects to change the state of their motion.

Inertia is the natural tendency of an object to remain at rest or in motion at a constant velocity along a straight line. Inertia

An object will have inertia proportional to its mass, measured in kilograms. This means the more the mass of an object, the greater its inertia. In this way, mass is the quantitative measurement of an object's inertia, whether at rest or in motion.

So Newton's first law can be summarised as the law of inertia. In the absence of a net force, an object will remain in its state of motion, whether at rest or moving with constant velocity. The sum of multiple forces acting on an object is called the net force. If the net force is zero, there will be no acceleration. This can be modelled mathematically as F = 0.

We are only going to deal with coordinate systems that do not accelerate. They are called inertial reference frames. They are either at rest or moving with constant velocity (accelerating reference frames). A good example of inertia at work is when passengers fall forward when a fast-moving bus stops suddenly.

## What is the importance of Newton's first law?

As discussed earlier, Newton's first law can be considered as the law of inertia. This is very significant – it is what holds the universe together. If inertia were to be turned off, everything would fall apart.

Remember that net force is the addition of all the forces that act on an object. All the forces considered here exist on Earth. It is quite different in space. Since there is almost no other force acting on bodies in space, they keep moving and could be moving forever. So Newton's first law gives us an understanding of the movements of bodies in space.

This same law makes it possible for us to develop cars by knowing how much force it will take to get the car to move and how much it will need to stop it. The heavier the car, the more force it will require. This isn't just the case with cars but ships, bicycles, machines, rockets, etc.

Newton's First Law - Key takeaways

• Newton's first law of motion states that a body will stay at a constant velocity unless acted upon by an external force.
• Inertia is the natural tendency of an object to remain at rest or in motion at a constant velocity along a straight line.
• An object is compelled to stay in motion till it encounters a net force.
• Newton's first law can be summarised as the law of inertia.
• There will be no acceleration if the net force is 0.
• An object's inertia is proportional to its mass.

## Frequently Asked Questions about Newton's First Law

Newton's first law of motion states that a body will stay at a constant velocity unless acted upon by an external force.

Driving a car and then braking suddenly will stop the car, but the people inside will keep moving until they are pulled back by their seatbelts.

Newton's second law of motion states that the time rate of change of the momentum of a body is equal in both magnitude and direction to the force imposed on it.

Newton's third law of motion states that when two bodies interact, they apply forces to one another that are equal in magnitude and opposite in direction.

A rocket will remain motionless on a launchpad till a force is exerted for it to move upward.

## Final Newton's First Law Quiz

Question

What is Newton's first law?

Newton's first law of motion states that a body will stay at a constant velocity unless acted upon by an external force.

Show question

Question

Which of these is an example of the presence of the first law of motion?

A ball at rest will continue to be motionless until someone kicks it, or some other force acts on it.

Show question

Question

Which law is known as the law of inertia?

Newton's first law of motion.

Show question

Question

Inertia is the natural tendency of an object to remain at rest or in motion at a constant velocity along a straight line.

True

Show question

Question

When does net force = 0?

When a body is in equilibrium.

Show question

Question

What is net force?

Net force is the vector sum of all the forces that act on an object.

Show question

Question

Can net force be equal to zero?

Yes, when it is in equilibrium

Show question

Question

A vector sum of all the forces that act on the object is what ...?

Net force

Show question

Question

When an object's acceleration is zero and velocity is at rest, it ....?

Stays at rest

Show question

Question

People experience a jerk when a moving bus stops due to what law of motion?

Newton's first law of motion

Show question

Question

What causes the motion of a body which was initially at rest?

Force

Show question

Question

Which of these does Newton's first law best describe?

Inertia

Show question

Question

In which of these cases is net force not equal to zero?

A free-falling ball

Show question

More about Newton's First Law 60%

of the users don't pass the Newton's First Law quiz! Will you pass the quiz?

Start Quiz

### No need to cheat if you have everything you need to succeed! Packed into one app! ## Study Plan

Be perfectly prepared on time with an individual plan. ## Quizzes

Test your knowledge with gamified quizzes. ## Flashcards

Create and find flashcards in record time. ## Notes

Create beautiful notes faster than ever before. ## Study Sets

Have all your study materials in one place. ## Documents

Upload unlimited documents and save them online. ## Study Analytics

Identify your study strength and weaknesses. ## Weekly Goals

Set individual study goals and earn points reaching them. ## Smart Reminders

Stop procrastinating with our study reminders. ## Rewards

Earn points, unlock badges and level up while studying. ## Magic Marker

Create flashcards in notes completely automatically. ## Smart Formatting

Create the most beautiful study materials using our templates.

Sign up to highlight and take notes. It’s 100% free.