Newtons Laws?

Question

Can anyone give me easy definitions for the three laws and one example for each please? Much appreciated as I want to grasp the laws before moving to AS Physics

It's not my homework lol it's July no one is in school

Answer 1

First law-Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it-anything wont move until u do something to make it move-oranything is moving unless u make something that changes this movement

second law-The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors ,in this law the direction of the force vector is the same as the direction of the acceleration vector. -force and accelration are resolved in the same direction(if u dont get this its ok,its omething u'll lkearn deeply in mechanics later),so since they r in the same direction, and r proportional to mass thus f=ma

third law-For every action there is an equal and opposite reaction-if u hit something it 'll go the way u hit it,u made the action, and it going the other way is the reaction, throwing a rubber ball at the wall,the acion is the ball hitting the wall, the reaction is the rubber ball coming back

hope i made it simple

Answer 2

A push or pull is called force in Physics.

A body is at rest if its speed is zero: it is in uniform motion if its speed is constant.

The first is called state of rest and the second one is state of uniform motion.

A force (push or pull) is always necessary to move a body from rest.

The above statement is familiar to every one.

Therefore, if a body is at rest it will always be at rest unless a force acts on it .

This is Newton’s one part of First law.

The second part says that if an object is in uniform motion it will be always in uniform motion unless a force acts on it.

To understand this statement some imagination needs.

We push a plate from one edge of a table to the other edge. It moves some distance and then stops. This is due to the force called friction. The table is made smooth, the plate will move some what greater distance and then it will stop. We cannot avoid friction altogether. But we can infer that if there is no friction at all then there is nothing to stop the plate from moving and it will continue to move.

However, if it slows down, we say certainly there is some force to slow it down.

The second part of Newton’s first law, “a body in uniform motion will always be in uniform motion unless a force acts on it” is understood now.

Once a force acts on a body the speed of the body not only changes, but is continuously changing as long as the force acts.

That is speed is zero first, then the speed increases depending upon the force, say to 10m/s in the first second , then it increases to 20m/s in the second second, then to 30m/s in the third second and so on increases for ever as long as the force acts.

Another thing is if the same force is applied to different bodies then the rate of change of velocity (we call it as acceleration) is different for different bodies.
This is due to the masses of the body. Mass of one body is different from the other.
If masses were same then the acceleration will also be the same.
Thus the force is equal to the product of mass and acceleration. The motion is also in the direction of force.

This is Newton’s second law. It states, “Force is equal to mass times acceleration”

The product of mass and velocity is called momentum. Newton’s second law can also be stated as force is equal to the rate of change of momentum. But that is for a special case when the mass of body in motion is changing.

In the beginning we said that a push or pull is force and a force is necessary to change the state of a body.

Suppose a body A gives a force on B, We have seen B’s state is altered. But we have forgotten or we have not cared what will happen to A.

If A pushes B, it implies B pushes A. If A pulls B, it implies B pulls A.

Without the other there is no meaning of force. Force always exists in pairs.

What all happens to B, because of A, is also happening to a because of B.

This is Newton’s third law. It states, “If a body exerts a force on another body then the second will exert same but opposite force on the first body.”

The example for third law is numerous because wherever we come across force we can always find the other force of this pair of forces.

We walk because we push back the ground, the ground pushes us forward.
We swim in water because we push water back and water pushes us in front.
A heavy object is not moving if we apply force. This is because friction pulls us in the opposite direction.

Answer 3

well,for motion,in newtonian mechanics,there are 3 laws-------------------------law no. one: nothing in this 3-d world has enough tendency to change its state of motion,rest or direction.

law no. two: force is a push or pull that changes momentum of a body(whether angular or linear)

law no three: to every action there is always a reaction and the action and reaction are on different bodies.

there is a law for gravitation------- it states that every particle in the universe attaracts the other one by a force directly proportional to the product of the masses of both particles and inversely proportional to the square of the distance between them.

note that these laws are USELESS in quantam mechanics

Answer 4

1st law of motion--law of inertia..

all aojects at rest remained at rest or, if moving, witha constant velocity when no resltant forces acts on it.

2nd law of motion. rate of chage of momentum is proportional to the direction of force applied. it's nt F=MA, but F=M(V-U)/T..to be specific

3rd law.
for every force applied, there is always an equal and opposite force (action-reaction pairs)

Answer 5

http://www.physicsclassroom.com/Class/newtlaws/newtltoc.html

Answer 6

are we doing your home work???

Have you tried searching for it on yahoo or google