Laboratory Activity 13: Conservation of Energy and Circular Motion

Experimental Section

(1) You must first make sure that your force sensor is zeroed properly. With

nothing attached to the sensor, start the Capstone software. Decline any

suggested upgrades. Display a plot showing the force measured by the

sensor as a function of time, and set the sampling rate to 100 Hz.

(2) Start taking data by hitting the 'Start' button. You should see a line being

drawn (close to zero). While the line is being drawn, hit the 'zero' button

on the force sensor. The line should now be right on the horizontal axis

(if it wasn't there already). After zeroing the sensor, stop taking data.

(3) Now attach your pendulum, and let it hang vertically. While it is at rest,

measure the variables H and L depicted in the diagram above. When you

measure these, measure to the center of your pendulum mass.

(4) After measuring the values above, start the software and measure the

tension in the pendulum string when the mass is at rest. Record this

below.

(5) Now restart the software, displace the pendulum by approximately 45°,

and let it swing. If you are "coordinationally challenged", you may wish

to start it swinging first, and then start the software afterward. Sketch

below the tension in the string as a function of time.

(6) You are probably witnessing some variation in tension as the pendulum

swings. There are two distinct reasons for this variation. Provide a

qualitative explanation for the behavior you are seeing, identifying and

commenting upon both of these reasons.

(7) We now wish to determine experimentally the release height (y) that

causes the tension at the bottom of the are to be double what it was with

the pendulum at rest (Trest). You will need to make several measurements

here to get a reliable result. Fill in the blanks below:

(8) Once you have a good value for y, use your trigonometric magic to

determine the starting angle Odoub that causes the tension at the bottom to

be double its rest value.