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Moment of Inertia / Mass Contrasted

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Submitted by Rich on Mon, 04/22/2019 - 15:32

Introduction to Moment of Inertia

There are numerous analogies when comparing linear and rotational motion.  At the heart of these comparisons lie the concepts of mass on one hand and moment of inertia on the other.  In addition to being a property of any physical object, mass is a measure of the resistance of an object to acceleration when a net force has been applied to the object.  Newton's Second Law of Motion expresses this in the fa

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The "Speeder Upper" - Translational and Rotational Motion Study

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Submitted by Rich on Wed, 04/17/2019 - 19:08

What's a "Speeder Upper"?

As shown in Figure 1, a "Speeder Upper" is a pair of disks that are connected by a short rod of much smaller radius.  The NSTA science ruler gives you a feel for the dimensions of the Speeder Upper.  The disks are 0.5" thick and 2.5" in diameter and are connected by a short 5/16" diameter wood dowel rod.  The 3D printer stl file for the disks is provided with this lesson in the event that you want to make a Speeder Upper for use in your physics classroom.

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Brownian Motion: Order from Chaos

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Submitted by Rich on Fri, 03/15/2019 - 02:27

Brownian Motion

Brownian motion can be defined as the random motion of particles in a liquid or gas caused by the bombardment from molecules in the containing medium.  Have you ever looked at dust particles in the sunlight shining through a window?  They appear to move about randomly, even defying gravity.  This is an example of Brownian motion in which the dust particles are bombarded on all sides by gas molecules in the air.  Other examples of Brownian motion include the motion of grains of pollen on the surface of still water, the dif

Ideal Gas Law Verified in a Steel Balls Lab

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Submitted by Rich on Tue, 03/05/2019 - 22:18

Introduction to the Ideal Gas Law

The ideal gas law is commonly seen in the form PV = nRT, where P is the pressure, V is the volume, T is the absolute temperature, n is the amount of the gas in moles, and R is the ideal gas constant.  It is a composite form of Boyle's, Charles's, Avogadro's, and Gay Lussac's laws.  This law helps to explain how many things work, including bicycle pumps, hot air balloons, pressure cookers, and steam engines, just to mention a few.

Moment of Inertia Challenge

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Submitted by Rich on Sat, 02/23/2019 - 22:18

Introduction to the Moment of Inertia Challenge

We are going to assume that you have studied the concepts of moment of inertia and physical pendulums in your physics class.  With that in mind, we present a "Moment of Inertia Challenge" for you in this lab.  As you know, moment of inertia depends not only on the mass of an object, but also on how the mass is distributed, as well as the specific axis upon which it rotates.  It is of particular interest to compare the moments of inertia of two objects with the same mass but having the mass dist

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How does a Rangefinder Work - Physics of Probeware

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Submitted by clifton on Tue, 02/19/2019 - 04:34

Introduction to Rangefinders

Rangefinders, sometimes called motion sensors or motion detectors are commonly used in probeware, camera autofocus, and robotics. Rangefinders operate on the principle of a time-of-flight measurement and consist of a transmitter and receiver. The transmitter emits a signal (ultrasonic or optical) then the receiver detects the reflection or echo of the signal. The amount of time between transmit and receive is called the time-of-flight and is used to calculate the distance to the reflecting object:

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Moment of Inertia vs. Mass

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Submitted by Rich on Sun, 02/17/2019 - 21:06

Introduction to Moment of Inertia

There are numerous analogies when comparing linear and rotational motion.  At the heart of these comparisons lie the concepts of mass on one hand and moment of inertia on the other.  In addition to being a property of any physical object, mass is a measure of the resistance of an object to acceleration when a net force has been applied to the object.  Newton's Second Law of Motion expresses this in the familiar equation F = ma.  By analogy, the moment of inertia of any rigid obj

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Physical Pendulum: Finding Moment of Inertia

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Submitted by Rich on Tue, 02/12/2019 - 18:22

Introduction to the Physical Pendulum

Mount any rigid body such that it can swing in a vertical plane about an axis passing through the body.  You have constructed what is known as a physical pendulum.  The video below shows an example of such a pendulum.  In this video, a rigid circular body is swinging about an axis very close to the edge of the circle.  The circle was cut from a piece of cardboard.  PocketLab Voyager is resting at the bottom of a ring stand directly below the pivot point of the pendulum.  A tiny magnet has been attached to the bottom of the ci

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Thermal Energy Particle Motion Experiment

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Submitted by PocketLab on Sat, 02/09/2019 - 00:28

How does adding thermal energy effect the particle motion of a gas? 

Thermal Energy Examples

Matter makes up everything around us. The air we breathe, the water we drink, the chair we are sitting on, the cells in our body, it is all made up of matter. Matter can exist in different states: Take water for example, it can exist as a solid (an ice cube), liquid (water in a cup for drinking), and gas  (vapor rising from a boiling pot of water). In all three states, water is always made of the same molecules, H20, and the difference is the amount of thermal energy.

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