Force and Newton’s Laws of Motion

10 Questions

90 Seconds

90% to Pass

Register to view full lesson

You'll also get unlimited access to all the lessons in Math, English, Science, and more as a member. Plus, get practice tests, quizzes, and the progress tracker to view progress and achievements.

Create Your Account
A push or pull is called force, and force is required to change the motion of an object.

Example: The force we put on the paddles of the bicycle makes it move. Always the force has a size and direction (the size called Magnitude). Forces can make an object in motion, change the speed and change the direction of motion.
Force we put on the paddles of the bicycle
Force doesn't mean that it has to be moving from one location to another. Changing the shape of something also can be because of force.

Example: Squeezing an empty water bottle until it crumbles.
Force we put on the paddles of the bicycle


There are instances that on an object has more than one force. This combination of all of the forces acting on an object is called the NET FORCE

Example: The door of a fridge. It has a magnet, holding the magnetic force, and we exerting force on the magnet to open the door.

By adding all of the forces on an object together, calculate the net force.

Calculate the net force

Like velocity and acceleration, the force has direction. The direction needs to take care of when calculating the net force.

We add them if the forces are in the same direction, and we subtract them if the forces are in opposite directions.
Opening a door
The force was figured out by Isaac Newton.

Newton(N) is the SI unit for the force, which used his second name.

The force needed to accelerate an object with a mass of 1 kilogram at 1 meter per second squared equal to one newton (1N).

Newton formula

Example: About 1N of force is required to hold up an apple against the force of gravity.
Isaac Newton


Isaac Newton came up with the laws of motions, and from those, he described the motion of all objects in the universe.
NEWTON'S FIRST LAW OF MOTION - "An object in motion will remain in motion, and an object at rest will remain at rest unless there is a net force acting on the object."
Newton's first law of motion
Example: A ball is lying on a football pitch. It will remain in the same place until a player kicking the ball. This means it will remain the same unless an outside force acts on the ball. Assume the ball is in motion. It will remain in motion unless an outside force acts on it. That means the ball is in motion unless it stops because of friction between the ball and the grass, gravity, air resistance, or another player stopping the ball with his foot. If not, the ball would keep going without stopping.

Inertia and Momentum

Matter, if it is in motion, it likes to stay in motion, and if it is at rest, it is willing to remain at stay because the matter is not ready to change what it's doing.
Matter's resistance to change in motion is called INERTIA.
Newton's first law is sometimes referred to as the law of inertia because the matter will remain at rest or in constant motion unless acted on by an outside force.
Example: Assume; you are catching a soft cricket ball and then again a leather cricket ball. If they have the same velocity, it is easier to stop the motion of the soft cricket ball because the soft cricket ball has less mass than the leather cricket ball. That because an object with more mass has more inertia.
The measure of how difficult it is to change the inertia of an object is called momentum.

{momentum = mass × velocity}

Inertia and Momentum

From the second law of Newton's, he says the more force applied to and object, the faster it will accelerate. Further, the more mass an object has, the more force you will need to accelerate it.

Newton's secound law of motion
NEWTON'S SECOND LAW OF MOTION - "The acceleration of an object is equal to the net force on an object divided by the object's mass."
We can express the relationship between force and acceleration like below.
Acceleration formular
Formula to find the net force

{net force = mass × acceleration}

Example: Assume you apply the same amount of force and push a empty shopping cart and a shopping cart full with good. The empty cart will zoom off, but the heavy cart won't move. A larger mass will accelerate less if the same amount of force is applied.
Either speed up or slow down is something that causes a force.
The object will speed up when the net for is in the same direction as the velocity.
When you are running a race with the wind at your back, the net force is in the same direction, so you accelerate forward - Unbalanced force.
The project will slow down when the next force is in the opposite direction
When you run a race against the wind, the net force is pushing in the opposite direction, so you slow down - Balanced Force.
The equal size of the force and opposite direction of the force refers to Newton's third law.

Newton's third law of motion
NEWTON'S THIRD LAW OF MOTION - "Forces act in pairs: For every action, there is an equal but opposite reaction."

Example: Assume you are pushing a heavy shopping cart forward. You can probably push it a few feet, and you feel it also pushes you backward.
Newton's third law refers to the equal size of the force and opposite direction of the force. The size of the force on the bowling ball equals the size of the force on the body.

These coupled forces are called Action-Reaction pairs. They have equal but opposite forces.

Check Your Knowledge

Start Quiz