Centripetal Motion
What is a Force?
A force is a push or a pull on an object. When forces are applied, they are able to change the direction and velocity of a particular object and subsequently its acceleration as well. They are considered to be vector quantities, where they have both a magnitude and a direction, and are measured in Newtons (N).
Newton's Three Laws of Motion
Sir Isaac Newton proposed three laws to describe how objects move. These laws describe classical mechanic properties in the world.
Newton's First Law
When in an inertial reference frame, objects will remain at rest or continue to move at a constant velocity if no external force is applied.
In the figure on the side, diagram a represents how when no force is being applied, there is no movement on the block and it will remain at rest until some external force is applied. In diagram b, even though there is a force being applied onto an object, there is an equal magnitude force being applied in the opposite direciton of the friction force. Thus there is no movement. In diagram c, the force applied is greater than the force of friction, now the block is going to move.
(a)
(b)
(c)
F stands for the friction force and F stands for the applied force
fr
A
Newton's Second Law
Newton's second law can be described by a simple formula:
F=ma
F describes the force. It is a vector, which means that it requires both a magnitude and a direction. This property is measured in Newtons (N)
m describes the mass of the object that the force is being applied onto. The SI units for mass is kilograms (kg)
a represents the acceleration of the object. It is measured in meters per second squared (m/s )
2
Newton's Third Law
Newton’s third law states that for every action, there is an equal and opposite reaction. Subsequently, if we were to look at the net force of these two reactions, there would be a net force of zero; this is otherwise known as conservation. Conservation states that the net force that is exerted onto an object turns out to be zero.
Newton's third law can be described with this equation:
F = -F
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