A look at Newton’s Laws of Motion

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Lets first take a look at Newton’s Laws of Motion. These are:

First law: law of inertia.

Every body perseveres in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed.

There exists a set of inertial reference frames relative to which all particles with no net force acting on them will move without change in their velocity. This law is often simplified as “A body persists its state of rest or of uniform motion unless acted upon by an external unbalanced force.”

Second law

The change of momentum of a body is proportional to the impulse impressed on the body, and happens along the straight line on which that impulse is impressed.

Observed from an inertial reference frame, the net force on a particle of constant mass is proportional to the time rate of change of its linear momentum: F = d(mv)/dt. This law is often stated as, “Force equals mass times acceleration (F = ma)”: the net force on an object is equal to the mass of the object multiplied by its acceleration.

Third law: law of reciprocal actions

For a force there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions.

Whenever a particle A exerts a force on another particle B, which in turn simultaneously exerts a force on A with the same magnitude in the opposite direction. The strong form of the law further postulates that these two forces act along the same line. This law is often simplified into the sentence, “To every action there is an equal and opposite reaction.”

These three physical laws form the basis for classical mechanics and of our understanding of motion.

Now lets take each law one at a time and try to understand what they mean and how they are relevant to us in everyday life.

First law

It says that the state of an object changes when a greater force is applied.

Second law

It says that the speed at which the object moves is proportional to the force applied to it.

Third law

The best way for me to explain this is to use: Every action has an equal and opposite reaction.

Now I have introduced you to the laws that govern movement lets look at how these laws effect us in every day life and when doing sports.

The laws of motion and rowing.

To move the boat through the water you need to apply a force in the opposite direction to which you wish to move. This movement is achieved through the use of oars.

To speed up the boat the rower applies more force to the oars and speeds up their stroke.


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