Three Laws of Motion

Wellvei-Ann A. Valois

IV-Effeciency

Mrs. Bongay

Three Laws of Motion

Melody A. Asmole

IV-Effeciency

Mrs. Bongay

Three Laws of Motion

Connie Chelle B. Lucero

IV-Effeciency

Mrs. Bongay

Three Laws of Motion

Zuharda W. Dading

IV-Effeciency

Mrs. Bongay

Three Laws of Motion

Ma. Rowena A. Jarabece

IV-Effeciency

Mrs. Bongay

Newton’s Laws of Motion

Newton’s First Law: Law of Inertia

According to Newton, an object

Newton’s Second Law: Law of Acceleration

Newton’s Third Law: Law of Interaction

Newton’s Laws of Motion

Newton’s First Law: Law of Inertia

I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

ExamplesBalanced forces: As mentioned above, balanced forces are ones that do not create motion. One example is tug

of war. As one side pulls on the other, there is sometimes no motion at all. But there are forces are work. Those

forces are balanced and so even though there is force, there is no motion.

Unbalanced forces: These are the forces that cause movement. In the example above, the forces were

balanced and so there was no motion. However, if one team pulled harder than the other, there would be motion.

Objects at rest: If unbalanced force causes motion, then you are probably wondering how to describe the motion

that occurs from and object at rest being moved. For example you may push a piano and it may not move. That is

because the force of gravity uses the weight of the piano as a type of force that keeps balance unless an outside

force or external force creates an imbalance. The harder you push, the more of a chance you have of creating an

unbalanced force. If you push hard enough you will create an unbalanced force and the piano will move.

This review should have helped you to understand Newton's First Law of Motion.

 Explanation: An object will remain at rest or in uniform motion in a straight line unless acted on by an external unbalanced force.

Newton’s Second Law: Law of Acceleration

II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

If we increase the amount of net force than the acceleration also increases in the same amount. If

we decrease the net force than acceleration also decreases. Let’s see it from the given picture

below.

 

 

In the Picture given above we double the force than the magnitude of acceleration also becomes

double. On the contrary we decrease the force then, acceleration also decreases. We understand

the relation between force and acceleration. Well, do you think mass affects the acceleration?

Suppose that you push a box that is empty, you can easily push it. If the box is full, then can you

push it easily with the same force? The answer is of course “NO”. All you experience this in your

daily life. Bigger the mass results in bigger the force. Thus, we find another relation of force which

is;

We found two relations of force. Now it is time to combine them.

Force is linearly proportional to the mass and acceleration. If the mass is constant, when we

increase the force the object gains acceleration with the same amount or, if the force is constant,

when we decrease the mass acceleration increases with the same amount. 

ExampleWhere, F is the force and its unit is Newton, m is mass and has the unit kg and a is

the acceleration has unit m/s².Newton’s Third Law: Law of Interaction

III. For every action there is an equal and opposite reaction.

A variety of action-reaction force pairs are evident in nature. Consider the propulsion of a fish through the water. A fish uses its fins to push water backwards. But a push on the water will only serve to accelerate the water. Since forces result from mutual interactions, the water must also be pushing the fish forwards, propelling the fish through the water. The size of the force on the water equals the size of the force on the fish; the direction of the force on the water (backwards) is opposite the direction of the force on the fish (forwards). For every action, there is an equal (in size) and opposite (in direction) reaction force. Action-reaction force pairs make it possible for fish to swim.

Consider the flying motion of birds. A bird flies by use of its wings. The wings of a bird push air downwards. Since forces result from mutual interactions, the air must also be pushing the bird upwards. The size of the force on the air equals the size of the force on the bird; the direction of the force on the air (downwards) is opposite the direction of the force on the bird (upwards). For every action, there is an equal (in size) and opposite (in direction) reaction. Action-reaction force pairs make it possible for birds to fly.

Consider the motion of a car on the way to school. A car is equipped with wheels that spin. As the wheels spin, they grip the road and push the road backwards. Since forces result from mutual interactions, the road must also be pushing the wheels forward. The size of the force on the road equals the size of the force on the wheels (or car); the direction of the force on the road (backwards) is opposite the direction of the force on the wheels (forwards). For every action, there is an equal (in size) and opposite (in direction) reaction. Action-reaction force pairs make it possible for cars to move along a roadway surface.

 

Newton’s Laws of Motion

Newton’s First Law: Law of Inertia

An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

This law is often called "the law of inertia".

This means that there is a natural tendency of objects to keep on doing what they're doing. All objects resist changes in their

state of motion. In the absence of an unbalanced force, an object in motion will

maintain this state of motion.

Newton’s Second Law: Law of Acceleration

Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).

Everyone unconsiously knows the Second Law. Everyone knows that heavier objects require more force to move the same distance as lighter objects.

However, the Second Law gives us an exact relationship between force, mass, and acceleration. It can be expressed as a mathematical equation: 

 or 

FORCE = MASS times ACCELERATION

This is an example of how Newton's Second Law works:

Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.05 m/s/s. Using Newton's Second Law, you can compute how much force Mike is applying to the car.

 

Answer = 50 newtonsNewton’s Third Law: Law of Interaction

For every action there is an equal and opposite re-action.

This means that for every force there is a reaction force that is equal in size, but

opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the opposite direction

equally hard. 

Let's study how a rocket works to understandNewton's Third Law. 

The rocket's action is to push down on the ground with the force of its powerful engines,

and the reaction is that the ground pushes the rocket upwards with an equal force.

UP, UP, and AWAY!

Newton’s Laws of Motion

Newton’s First Law: Law of Inertia

First LawThe first law says that an object at rest tends to stay at rest, and an object in motion tends to stay in motion, with the same direction and speed. Motion (or lack of motion) cannot change without an unbalanced force acting. If nothing is happening to you, and nothing does happen, you will never go anywhere. If you're going in a specific direction, unless something happens to you, you will always go in that direction. Forever. 

You can see good examples of this idea when you see video footage of astronauts. Have you ever noticed that their tools float? They can just place them in space and they stay in one place. There is no interfering force to cause this situation to change. The same is true when they throw objects

for the camera. Those objects move in a straight line. If they threw something when doing a spacewalk, that object would continue moving in the same direction and with the same speed unless interfered with; for example, if a planet's gravity pulled on it (Note: This is a really really simple way of descibing a big idea. You will learn all the real details - and math - when you start taking more advanced classes in physics.). 

Newton’s Second Law: Law of Acceleration

Second LawThe second law says that the acceleration of an object produced by a net (total) applied force is directly related to the magnitude of the force, the same direction as the force, and inversely related to the mass of the object (inverse is a value that is one over another number... the inverse of 2 is 1/2). The second law shows that if you exert the same force on two objects of different mass, you will get different accelerations (changes in motion). The effect (acceleration) on the smaller mass will be greater (more noticeable). The effect of a 10 newton force on a baseball would be much greater than that same force acting on a truck. The difference in effect (acceleration) is entirely due to the difference in their masses. 

Newton’s Third Law: Law of Interaction

Third LawThe third law says that for every action (force) there is an equal and opposite reaction (force). Forces are found in pairs. Think about the time you sit in a chair. Your body exerts a force downward and that chair needs to exert an equal force upward or the chair will collapse. It's an issue of symmetry. Acting

forces encounter other forces in the opposite direction. There's also the example of shooting a cannonball. When the cannonball is fired through the air (by the explosion), the cannon is pushed backward. The force pushing the ball out was equal to the force pushing the cannon back, but the effect on the cannon is less noticeable because it has a much larger mass. That example is similar to the kick when a gun fires a bullet forward. 

Newton’s Laws of Motion

Newton’s First Law: Law of Inertia

Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This is normally taken as the definition of inertia. The key point here is that if there is no net force acting on an object (if all the external forces cancel each other out) then the object will maintain a constant velocity. If that velocity is zero, then the object remains at rest. If an external force is applied, the velocity will change because of the force.

Newton’s Second Law: Law of Acceleration

The second law explains how the velocity of an object changes when it is subjected to an external force. The law defines aforce to be equal to change in momentum (mass times velocity) per change in time. Newton also developed the calculus of mathematics, and the "changes" expressed in the second law are most accurately defined in differential forms. (Calculus can also be used to determine the velocity and location variations experienced by an object subjected to an external force.) For an object with a constant mass m, the second law states that the force F is the product of an object's mass and its acceleration a:

F = m * a

Newton’s Third Law: Law of Interaction

For an external applied force, the change in velocity depends on the mass of the object. A force will cause a change in velocity; and likewise, a change in velocity will generate a force. The equation works both ways.

The third law states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exerts an equal force on object A. Notice that the forces are exerted on different objects. The third law can be used to explain the generation of lift by a wing and the production of thrust by a jet engine.

Second law examples

Third law

First law