The concept of force was created to quantify the interaction between 2 objects. Force is regarded as a vector because it has a magnitude and is exerted in a specific direction. Force is most easily measured by utilizing a spring - when we stand on a spring scale, it is merely measuring the force of our weight due to gravity pressing against it. By measuring how much a spring compresses when a force is applied we can obtain a very accurate measurement - an equation found (link to post) here.
Force is largely measured in newtons (N). 1 N is approximately the downward gravitational force of the Earth on a small apple (Newton formulated the idea of gravity by watching an apple fall from a tree, what a coincidence).
Force is the derivative of momentum, described as "the instantaneous time rate of change of the momentum of an object is equal to the net force acting on the object," or more simply, "the derivative of the momentum with respect to time is equal to the net force acting on the object."$$\frac{d\vec{p}}{dt} = \vec{F}_{net}$$
The net force ($\vec{F}_{net}$) is widely used in physics to describe all the forces acting on a system: $$\vec{F}_{net} = \sum\limits_{i=1}^n \vec{F}_i$$
Showing posts with label net force. Show all posts
Showing posts with label net force. Show all posts
Wednesday, March 6, 2013
Momentum Principle
The Momentum Principle is Newton's Second Law - a fundamental principle of physics. It is used to predict the behavior of objects, restating Newton's First Law in a form that is measurable and causal. $$\Delta\vec{p} = \vec{F}_{net}\Delta t$$This equation simply states that: The change in momentum ($\Delta\vec{p}$) is equal to the net force ($\vec{F}_{net}$) times the elapsed time ($\Delta t$).
This is only effective if the net force is nearly constant. So, either the net force must be constant, or the measurement used in increments of time that are small enough to model nearly constant force.
For instance, if we had a net force that changed at $t=3$ and $t=7$, respectively, we could make the measurement from $t=0$, $\Delta\vec{p} = \vec{F}_{net}\times3$, and then again from $t=3$ as $\Delta\vec{p} = \vec{F}_{net}\times4$ to conclude at $t=7$.
This is only effective if the net force is nearly constant. So, either the net force must be constant, or the measurement used in increments of time that are small enough to model nearly constant force.
For instance, if we had a net force that changed at $t=3$ and $t=7$, respectively, we could make the measurement from $t=0$, $\Delta\vec{p} = \vec{F}_{net}\times3$, and then again from $t=3$ as $\Delta\vec{p} = \vec{F}_{net}\times4$ to conclude at $t=7$.
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