23 July 2012

Newton's second and Third Laws of motion :In Book Principia

The Second Law of Motion : The Second Law describes what will happen if there is a force.
When an external, unbalanced force acts on an object, the object will accelerate in the same direction of  the force. Then,
The acceleration varies directly as the force,
=>  a F
This just means that if the force increases, the acceleration will increase. If the force decreases,
the acceleration decreases.
The acceleration varies inversely the mass
=>  a 1/m
This means that if the mass is bigger, the acceleration is less. If the mass is less, the acceleration is more.
=>  a F/m
=>  F = k ma Here k is a constant
=> F = ma
Hence, Force is equal to product of mass and acceleration
F = force (Newton, N)
m = mass (kg)
a = acceleration (m/s2)
By definition a one kilogram mass will be accelerated at 1 m/s2 if a 1 Newton force is applied to it.

Don't forget to turn the mass into kilograms when you solve numerical problems.

Newton's Third Law (Action-Reaction)

What happens when you have objects interacting, affecting each other?

“For every action force there is an equal and opposite reaction force.”

Action: the tires on a car push on the road…   Reaction: the road pushes on the tires.

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