PASCO ME-6828 Dynamics Cart Magnetic Damping User Manual

Page 10

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 3 : P r e d i c t i n g T e r m i n a l Ve l o c i t y

Equation 3 assumes that magnetic drag is the only source of friction. A real cart is
also affected by friction that is not proportional velocity, but is constant as long as the
cart is moving. If this additional frictional force is

, then the net force on the cart is

(eq. 4)

and

(eq. 5)

The addition of

does affect the slope of the

v versus a graph, but it does add a ver-

tical offset (or “Y-intercept’) equal to

In this part of the experiment, you will use the motion sensor to record

v and a as the

cart slows down after you push it on a level track.

Set-up

Make the track level.

Attach a motion sensor to the left end of the track.

Attach the Magnetic Damping Accessory to the cart.

If you are using a plastic cart, add about 250 g of mass, so that the total mass is
about 500 g. (Additional mass is not necessary with a metal cart.)

Place the cart on the track with the Magnetic Damping Accessory away from the
motion sensor.

Adjust the magnets to be about 1 mm above the track. Check to make sure that
the magnets do not touch the track when you push the cart swiftly.

Important: After you have adjusted the magnets, do not readjust them for the remainder of the
experiment.

Experiment set-up for Terminal Velocity, Part I

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.

Connect the sensor to your interface.

Prepare a graph (or graphs) to display Position, Velocity, and Acceleration versus
time.

Take some test data and adjust the sensor so that it can measure the cart’s position
up to a distance of about 1 m. Delete the test data.

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

net

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