PASCO ME-6828 Dynamics Cart Magnetic Damping - Manual (Page 6)

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D y n a m i c s C a r t M a g n e t i c D a m p i n g E x p e r i m e n t 2 : C r i ti c a l D a m p i n g
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3. Use tape or a pencil to mark the track about 50 cm above equilibrium.
4. Pull the cart up the track to the mark.
5. Let the cart go and carefully observe it’s movement as it comes to a stop. If the
cart overshoots equilibrium and comes back up the track, it is under-damped. If it
comes to a stop without overshooting, it is either over-damped or critically
damped.
6. Adjust the height of the magnets to reduce or increase the amount of damping.
7. Repeat steps 4 through 6 several times to find the least amount of damping (big-
gest gap) that will make the cart stop without overshooting. This is critical damp-
ing.
Method I (using a stopwatch)
Skip to Method II if you will be using a motion sensor.
1. Pull the cart up the track exactly to the mark.
2. Release the cart and start the stopwatch at the same time.
3. Stop the stopwatch when the cart stops.
4. Record the time.
5. Move the magnets up by about 1 mm to make the system under-damped.
6. Repeat steps 1 through 4.
7. Move the magnets down as close to the track as you can get them (without touch-
ing) to make the system over-damped.
8. Repeat steps 1 through 4.
Skip to the Question on page 7.
Method II (using a motion sensor)
Sensor, Interface, and Software Set-up
For detailed information about setting up your motion sensor, interface, and software, refer to the
instructions supplied with those products.
1. Place a motion sensor at the lower end of the track.
2. Connect the sensor to your interface.
3. Set the sampling rate to 50 Hz.
4. Prepare a graph to display Position versus time.
5. Take some test data and adjust the sensor so that it can measure the cart’s position
up to a distance of about 70 cm. Delete the test data.
Motion sensor at end of
track