conclusion on the project of Newtons laws of motion
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Answer:
Newton’s laws of motion are three physical laws that, together, laid the foundation for classical mechanics. They describe the relationship between a body and the forces acting upon it, and its motion in response to those forces. More precisely, the first law defines the force qualitatively, the second law offers a quantitative measure of the force, and the third asserts that a single isolated force doesn’t exist. These three laws have been expressed in several ways, over nearly three centuries,and can be summarised as follows:
First law: In an inertial frame of reference, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.
Second law: In an inertial reference frame, the vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration a of the object: F = ma. (It is assumed here that the mass m is constant – see below.)
Third law: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
Answer:
Newton's First Law of Motion
Every body continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it.
- Newton's First Law of Motion, translated from the "Principia"
This is sometimes called the Law of Inertia, or just inertia. Essentially, it makes the following two points:An object that is not moving will not move until a force acts upon it.
An object that is in motion will not change velocity (or stop) until a force acts upon it.
The first point seems relatively obvious to most people, but the second may take some thinking through. Everyone knows that things don't keep moving forever. If I slide a hockey puck along a table, it slows and eventually comes to a stop. But according to Newton's laws, this is because a force is acting on the hockey puck and, sure enough, there is a frictional force between the table and the puck. That frictional force is in the direction that is opposite the movement of the puck. It's this force which causes the object to slow to a stop. In the absence (or virtual absence) of such a force, as on an air hockey table or ice rink, the puck's motion isn't as hindered.
Here is another way of stating Newton's First Law:
A body that is acted on by no net force moves at a constant velocity (which may be zero) and zero acceleration.
So with no net force, the object just keeps doing what it is doing. It is important to note the words net force. This means the total forces upon the object must add up to zero. An object sitting on my floor has a gravitational force pulling it downward, but there is also a normal force pushing upward from the floor, so the net force is zero. Therefore, it doesn’t move.
To return to the hockey puck example, consider two people hitting the hockey puck on exactly opposite sides at exactly the same time and with exactly identical force. In this rare case, the puck would not move.
Since both velocity and force are vector quantities, the directions are important to this process. If a force (such as gravity) acts downward on an object and there's no upward force, the object will gain a vertical acceleration downward. The horizontal velocity will not change, however.
If I throw a ball off my balcony at a horizontal speed of 3 meters per second, it will hit the ground with a horizontal speed of 3 m/s (ignoring the force of air resistance), even though gravity exerted a force (and therefore acceleration) in the vertical direction. If it weren't for gravity, the ball would have kept going in a straight line...at least, until it hit my neighbor's house.
Newton's Second Law of Motion
The acceleration produced by a particular force acting on a body is directly proportional to the magnitude of the force and inversely proportional to the mass of the body.
(Translated from the "Principia")
The mathematical formulation of the second law is shown below, with F representing the force, m representing the object's mass and a representing the object's acceleration.
∑ F = ma
Newton's Third Law of Motion
To every action there is always opposed an equal reaction; or, the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.
(Translated from the "Principia")
We represent the Third Law by looking at two bodies, A and B, that are interacting. We define FA as the force applied to body A by body B, and FA as the force applied to body B by body A. These forces will be equal in magnitude and opposite in direction. In mathematical terms, it is expressed as:
FB = - FA
or
FA + FB = 0
This is not the same thing as having a net force of zero, however. If you apply a force to an empty shoebox sitting on a table, the shoebox applies an equal force back on you. This doesn't sound right at first — you're obviously pushing on the box, and it is obviously not pushing on you. Remember that according to the Second Law, force and acceleration are related but they aren't identical!