Dynamics of a trolley rails
THE UNIVERSITY OF HONG KONG
DEPARTMENT OF MECHANICAL ENGINEERING
Part I APPLIED DYNAMICS LAB (full report required)
DYNAMICS OF A TROLLEY ON RAILS
Based on document MGS/ID137/203 by Dr MG Sainsbury
Modified in Feb 2007 & Jan 2008 by Dr L Huang and Mr WS Sze
1. Objectives
(1) To measure the velocity and acceleration of a trolley as it descends on inclined track and is stopped by a nonlinear elastic arrester system.
(2) To compare the measured acceleration, velocity and displacement with theoretical predictions of various methods and discuss the physics learned.
2. Apparatus
The test setup comprises a short inclined railway track with a trolley that rolls down the rails and is stopped by a transversely mounted elastic cord at the bottom, as shown below:
Although the velocity and acceleration can be estimated approximately from measurements with a ruler and a stopwatch, it is more accurate to collect data automatically from a sensor. In this experiment, a magnetic sensor mounted underneath the trolley does the job. The sensor contains a small magnet surrounded by a coil. As the sensor moves over each edge of the steel sleeper, the field around the magnet suddenly changes, and this induces a sudden voltage across the coil. It generates two pulses every time it passes over one steel sleeper, one positive and one negative. Since all the sleepers are equi-spaced, a measurement of the time interval between successive pulses allows instantaneous velocities to be calculated.
The pulses could be viewed on an oscilloscope, but the screen would only be wide enough to look at
1 of 7
several pulses. To avoid this problem, and to analyze the results more thoroughly, the pulses are sampled as thousands of instantaneous voltages using an analog-to-digital converter (ADC) card in a computer. The information is stored in a file that can then be read by a specially written computer program called “ScrollGraph”. This program has a Windows® graphical user
DEPARTMENT OF MECHANICAL ENGINEERING
Part I APPLIED DYNAMICS LAB (full report required)
DYNAMICS OF A TROLLEY ON RAILS
Based on document MGS/ID137/203 by Dr MG Sainsbury
Modified in Feb 2007 & Jan 2008 by Dr L Huang and Mr WS Sze
1. Objectives
(1) To measure the velocity and acceleration of a trolley as it descends on inclined track and is stopped by a nonlinear elastic arrester system.
(2) To compare the measured acceleration, velocity and displacement with theoretical predictions of various methods and discuss the physics learned.
2. Apparatus
The test setup comprises a short inclined railway track with a trolley that rolls down the rails and is stopped by a transversely mounted elastic cord at the bottom, as shown below:
Although the velocity and acceleration can be estimated approximately from measurements with a ruler and a stopwatch, it is more accurate to collect data automatically from a sensor. In this experiment, a magnetic sensor mounted underneath the trolley does the job. The sensor contains a small magnet surrounded by a coil. As the sensor moves over each edge of the steel sleeper, the field around the magnet suddenly changes, and this induces a sudden voltage across the coil. It generates two pulses every time it passes over one steel sleeper, one positive and one negative. Since all the sleepers are equi-spaced, a measurement of the time interval between successive pulses allows instantaneous velocities to be calculated.
The pulses could be viewed on an oscilloscope, but the screen would only be wide enough to look at
1 of 7
several pulses. To avoid this problem, and to analyze the results more thoroughly, the pulses are sampled as thousands of instantaneous voltages using an analog-to-digital converter (ADC) card in a computer. The information is stored in a file that can then be read by a specially written computer program called “ScrollGraph”. This program has a Windows® graphical user