# Tagged With "Velocity"

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#### Using a 33-45-78 Turntable to Show that Centripetal Acceleration is Proportional to the Square of the Velocity and Inversely Proportional to Radius

PocketLab in conjunction with a 33-45-78 RPM turntable is an ideal setup for studying centripetal acceleration. There are two videos that can be found in the Videos page of this web site. They show that (1) keeping radius constant implies that centripetal acceleration is proportional to the square of the velocity, (2) keeping velocity constant while varying the radius implies that centripetal acceleration is inversely proportional to the radius. The PocketLab is placed in its silicone...

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#### PocketLab on a Skier's Edge Machine

The PocketLab is an ideal device for measuring user performance for a variety of exercise equipment. One example of such equipment is the Skier's Edge, whose company was founded in 1987. This machine was designed for non-impact lateral conditioning that simulates the experience of downhill skiing. The photo below shows the skiing machine. The skier stands on the two black platforms, holding poles and moves the carriage back-and-forth on the curved white tracks. A close-up view of the...

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#### PocketLab Joins Ozobot to Study Position, Velocity and Acceleration Concepts

Ozobot ( ozobot.com ) is a tiny one inch diameter line-traveling robot that can be used in conjunction with PocketLab to easily study the physics concepts of position, velocity, and acceleration and their time graphs. PocketLab is simply taped to the top of an Ozobot using double-sided mounting tape. In other words, Ozobot gives Pocket lab a ride. The photo below shows this setup, with Ozobot following a 1/4" heavy black line drawn with a chisel tip marking pen. A magnetic ruler can be...

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#### PocketLab Experiment on Centripetal Acceleration with a 3-speed Ceiling Fan

There are two approaches that the teacher can take to doing this experiment on centripetal acceleration with a three-speed ceiling fan and PocketLab. The first choice is for those with an available three-speed ceiling fan. In this case students can collect all data by actually performing the experiment themselves. The PocketLab should be mounted to one of the ceiling fan blades with a very strong double stick mounting tape. For safety, however, students should still wear goggles. The author...

Blog Post

#### Investigating the "Spinning Coin" (Euler Disk) Problem

Most everyone has spun a coin on its edge on a table top, and many find the result quite fascinating. The coin gradually begins to fall on its side while spinning, makes a whirring sound with increasing frequency the longer it spins, and then abruptly stops. The Swiss physicist, Leonhard Euler, studied this back in the 1700's. An educational toy, referred to as Euler's disk can now be purchased on-line and in hobby shops specializing in science. Such disks have been carefully engineered to...

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#### Re: Investigating the "Spinning Coin" (Euler Disk) Problem

Rich- Your lab made me think of a dynamics problem I had in grad school. I dug up my old textbook so I could share. We analyzed the motion of a similar spinning disk. It was one of the toughest dynamics problems I ever had to solve. You have to solve for a system of equations of the angular acceleration of the spinning disk and the linear acceleration of the disk's center of mass. Eventually the system of equations gets too cumbersome to solve by-hand and so we used a program called...

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#### Re: A Velocity Lab Experiment on Rolling Resistance

Thanks again for the great lesson, Rich!

Blog Post

#### A Velocity Lab Experiment on Rolling Resistance

Rolling resistance is a force that opposes the motion when an object rolls along a surface. In this experiment a coasting cylinder on a carpet gradually slows down and stops due to rolling resistance. The primary factor affecting rolling resistance here is deformation of the carpet as the cylinder rolls. Not all of the energy needed to deform the carpet is recovered when the pressure from the cylinder is removed. In other words, the effect is non-elastic. The purpose of this experiment is...

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#### The Physics of a Falling and Unrolling TP Roll

Yes, that's right--the physics of a falling and unrolling toilet paper roll. This experiment will give students practice in rotational motion of an object and translational motion of its center-of-mass. It will also involve both the kinematics and dynamics of the motion. While it can be done by use of the VelocityLab app, interpretation of the angular velocity data from the PocketLab app is much easier. The figure below shows the apparatus setup for this lab experiment. A ring stand is on a...

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#### Rotational Dynamics of a Falling Meter Stick

There is a well-known problem in rotational dynamics that involves a meter stick. The meter stick is held in a vertical position with one end on the floor. It is then released so that it falls to the floor. The end initially on the floor is not allowed to slip during the fall. Students are asked to derive an equation that predicts the angular velocity of the meter stick just before it hits the floor. The derivation involves many physics concepts including gravitational potential energy,...

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#### A PocketLab Experimental Analysis of a Yo-yo

The yo-yo, a toy with an axle connected to two disks and string wound on the axle, has been of fascination to many for centuries. It also offers a perfect opportunity to study angular velocity when a PocketLab has been attached to it. A graph of angular velocity vs. time of a yo-yo will require students to think carefully about the detailed behavior related to its motion. The author worked with a purchased $3 yo-yo, but found the results to be much clearer when attaching a PocketLab to a...

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#### An Experiment in Rotational Dynamics that Emphasizes the NGSS Science and Engineering Practices

Here is a PocketLab based project that will get your physical science and physics students involved in many of the Next Generation Science Standards, particularly in the NGSS science and engineering practices. Two wheels and a wood axle from the PocketLab Maker Kit are placed on a narrow inclined plane so that the red wheels overhang the sides of the inclined plane and the entire system rolls down on the wood axle without any slipping. When the wheels and axle get near the bottom of the...

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#### Using VelocityLab in an AP/College Physics Experiment Involving Rotational Dynamics

This experiment is designed for AP Physics and college physics students. It considers a solid cylinder of mass M and radius R that is rolling down an incline with a height h without slipping. Using energy and dynamics concepts, students first derive equations for (1) the speed of the center of mass of the cylinder upon reaching the bottom of the incline, and (2) the acceleration of the center of mass of the cylinder as it rolls down the incline. The free-body diagram at the center shows all...

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#### VelocityLab Investigation of Damped Harmonic Motion

This investigation shows how VelocityLab allows for a quick and easy demonstration of damped harmonic motion. The photo below shows the experiment setup as performed by the author. A jellied cranberry sauce can was selected as there is virtually no sloshing of the cranberry sauce as the can oscillates back-and-forth on a curved piece of laminate flooring. The center of the flooring is clamped down to the table with an adjustable wrench. The ends of the laminate flooring are raised a little...

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#### Re: VelocityLab Investigation of Damped Harmonic Motion

Another great lesson, Rich! Thanks for contributing.

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#### Re: Determining the Radius of Curvature of a Gradual Street Turn

Rich- this is such a great demo! I'm sorry the video sync output failed after the trials. We've got an app update coming soon that will fix the bug and update a few other features.

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#### Determining the Radius of Curvature of a Gradual Street Turn

This lesson is a physics application of PocketLab that allows students to determine the radius of curvature of a gradual turn on a street. A PocketLab mounted on the dashboard of a car records both the angular velocity and the centripetal acceleration of the car as it moves at a nearly constant speed around the curve. All of the required data for an example problem are contained in files attached to this lesson. Alternately, students can collect their own data. If the latter approach is...

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#### Conservation of Momentum When Two Carts "Explode"

Do you have two carts from the PocketLab Maker Kits? Do you have two PocketLabs? You probably have at least two students in your physics class with iPhones. Do they have the VelocityLap app installed on their iPhones? Then you have the major components for your students to investigate conservation of momentum when two carts on a track "explode". As shown in the picture below, each cart has a PocketLab mounted on one of its wheels, so that the z-axis is the axis of interest when the carts are...