Tagged With "force"

Blog Post

Investigating the "Spinning Coin" (Euler Disk) Problem

Rich ·
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

Clif ·
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

Robby ·
Thanks again for the great lesson, Rich!
Blog Post

A Velocity Lab Experiment on Rolling Resistance

Rich ·
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...
Blog Post

The Physics of a Falling and Unrolling TP Roll

Rich ·
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...
Blog Post

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

Rich ·
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...
Blog Post

A Quantitative PocketLab Study of Momentum, Impulse, and Force in the Collision of Two Carts

Rich ·
You don't need an expensive air track to do a quantitative study of momentum, impulse, and force involved in the collision of two carts. You can get very good results by the use of two PocketLabs, two iPhones, and a pair of carts from the PocketLab Maker Kit. 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 moving. You can only connect one PocketLab to an iPhone at time, thus the need for two...
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