PASCO ME-6828 User Manual

Instruction Manual

012-10242A

Dynamics Cart Magnetic Damping

ME-6828

Included Equipment Part Number

1. Magnetic Damping Accessory ME-6828

2. Keeper plate 648-10173

Required Equipment Part Number

PAScar, Plunger Cart, or Collision Cart ME-6950, ME-9430,

Aluminum Dynamics Track ME-6953

For other recommended equipment, see experiments starting on page 3.

or similar

ME-9454

Introduction

Use the Magnetic Damping Accessory to add drag to a PASCO dynamics cart. When the cart moves on an aluminum track, the accessory’s magnets generate eddy currents in the track, which cause an opposing magnetic field. The resulting drag force is proportional to the cart’s velocity. The amount of damping can be varied by changing the size of the gap between the magnets and the track.

This manual includes set-up instructions, three experiments (starting on page 3), and sample data (page 13).

Set-up

The Magnetic Damping Accessory attaches to a cart magnetically using the magnets built into the cart’s bumper. If your cart does not have bumper magnets, install them before using the Magnetic Damping Accessory. (See instructions included with your cart for bumper magnet installation.)

1. Remove the keeper plate from the Magnetic Damping Accessory and put it aside.

800-772-8700 www.pasco.com

Dynamics Cart Magnetic Damping Storage and Safety

2. Place the Magnetic Damping Accessory on the magnet-equipped end of the cart

as illustrated.

3. Place the cart on an aluminum track.

4. Slide the Magnetic Damping Accessory up or down to adjust the amount of

damping. The magnets should not touch the track.

To set a gap size that can be measured or reproduced, use a stack of cards as a gauge. Place the cards between the magnets and track as illustrated. Slide the Magnetic Damping Accessory down until the magnets contact the top card; then remove the cards. Use calipers to measure the thickness of the stack. For maximum damping, use a single card.

Storage and Safety

• The Magnetic Damping Accessory is shipped with a keeper plate attached to the magnets. The keeper protects the magnets and reduces the external magnetic field. Always store the Magnetic Damping Accessory with the keeper in

place.

• Use caution when replacing the keeper to avoid being pinched or chipping the magnets.

• Do not remove the magnets from the body of the Magnetic Damping Acces- sory. If the magnets are accidentally removed, replace them with caution. The poles of all three magnets should have the same orientation.

• Keep the Magnetic Damping Accessory away from computers and magnetic recording media.

stack of

cards

Qualitative Demonstrations

The effects of magnetic damping can be surprising. Use these demonstrations illustrate the phenomenon.

• Place a strongly damped cart on a track and ask students to move it by hand. When the cart is moved quickly, the damping force is easily detected.

• Raise one end of the track by a few centimeters. Set the Magnetic Damping Accessory for maximum damping and allow the cart to run down the track. With the track inclined just enough to overcome rolling friction, the cart will creep very slowly at a constant velocity.

ME-6828 Experiment 1: Damped Oscillation

Experiment 1: Damped Oscillation

Equipment Part Number

Dynamics Cart Magnetic Damping ME-6828

Motion Sensor (optional for Method II) PS-2103A

Cart

Aluminum Track

Harmonic Springs

1, 2

Adjustable End Stop

IDS Pivot Clamp

ME-6950, ME-9430, or ME-9454

ME-6953

ME-9803A

ME-8971

ME-9810

or similar

Large Table Clamp ME-9472

90 cm Rod ME-8738

These items are components of many PASCO dynamics systems.

This experiment works best with a spring, or combination of springs, with a constant between 1.0 N/m and 1.5 N/m.

or similar

Set-up

1. Set up the equipment as illustrated. Use two or three weak springs combined end-to-end.

cart

two or three springs end-to-end

end stop

Magnetic Damping

Accessory

Experiment set-up for Damped Oscillation

2. Adjust the angle of the track (or the position of the end stop) so that the cart’s equilibrium position is about 40 cm from the lower end of the track.

Method I (without sensors)

Skip to Method II if you will be using a motion sensor.

1. Place the Magnetic Damping Accessory on the end of the cart with a gap of 10 mm between the magnets and the track.

2. Tap the cart a few times so that it moves to its equilibrium position.

3. Pull the cart up the track and hold it 20.0 cm from equilibrium.

pivot clamp

rod

table clamp

Gap between magnets

and track

Dynamics Cart Magnetic Damping Experiment 1: Damped Oscillation

4. Release the cart.

5. Allow the cart to oscillate. Count (and write down) the number of down-up cycles

that the cart completes before stopping.

6. Repeat steps 3 through 5 with the gap set to 8 mm, 6 mm, 4 mm, and 2 mm, and with the magnets as close as possible to the track without touching.

Skip to the Questions section on page 4.

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. Adjust the angle of the track so that the cart’s equilibrium position is about 40 cm

from the sensor.

3. Connect the sensor to your interface.

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.

Leave the sample rate at the motion sensor’s default of 10 Hz.

Data Collection

1. Place the Magnetic Damping Accessory on the end of the cart with a gap of 10 mm between the magnets and the track.

2. Tap the cart a few times so that it moves to its equilibrium position.

3. Pull the cart up the track and hold it 20.0 cm from equilibrium.

4. Release the cart and start data recording at the same time.

5. Allow the cart to oscillate until it comes to a stop.

6. Stop data recording.

7. Repeat steps 3 through 6 to record data runs with the gap set to 8 mm, 6 mm,

4 mm, and 2 mm. Record a final data run with the magnets as close as possible to the track without touching.

Motion sensor at end of

track

Question

What is the effect of moving the magnets closer to the track?

ME-6828 Experiment 2: Critical Damping

Experiment 2: Critical Damping

Equipment Part Number

Dynamics Cart Magnetic Damping ME-6828

Stopwatch (for Method I)

ME-1234

or similar

Motion Sensor (for Method II)

1, 2

Cart

Aluminum Track

Harmonic Springs

Adjustable End Stop

IDS Pivot Clamp

1, 3

PS-2103A

or similar

ME-6950, ME-9430, or ME-9454

ME-6953

ME-9803A

ME-8971

or similar

ME-9810

Large Table Clamp ME-9472

90 cm Rod ME-8738

These items are components of many PASCO dynamics systems.

Either a plastic or aluminum cart will work; however, the lighter plastic cart allows a relatively greater amount of damping.

This experiment requires a spring or combination of springs with constant between 1.0 N/m and 1.5 N/m. If the spring constant is

too high, over damping will not be achievable.

or similar

Set-up

1. Set up the equipment as illustrated. Use two or three weak springs combined end-to-end.

end stop

two or three springs

end-to-end

cart

Magnetic Damping

Accessory

Experiment set-up for Critical Damping

2. Adjust the angle of the track (or the position of the end stop) so that the cart’s equilibrium position is about 20 cm from the lower end of the track.

pivot clamp

rod

table clamp

+ 10 hidden pages