PURPOSE:
To expose the student to new equipment and lab procedures. And to calculate the tension on a string supporting different masses.

INTRODUCTION:
Force is a vector quantity with both a magnitude and direction. Forces can be added together to produce a resultant force in a true vector manner. The tension on a string that supports a mass is a resultant force with an X and Y component. In the diagram below left, the brass mass is being pulled downwards by gravity (T_Y) while the metal rod pushes on the wooded dowel rod to the right (T_X). The diagram below right illustrates that these two vector forces can be added together to produce the Tension force shown.

During this lab you will construct 4 variations on the diagram shown above and use Newton scales to measure the forces involved.

An electronic balance is provided to mass objects during the lab and a protractor is used to determine the angles.

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Four different runs of this lab will be performed. 1) with the large mass and long string, 2) with the small mass and long string, 3) with the large mass and short string and 4) with the small mass and short string.

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The forces measured in this lab are accomplished by two Newton scales. The blue scale will measure the strings Tension where the red scale will measure the TX component of that tension.

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If you get into trouble and perform some procedure that causes the lab to fail(lab equipment will no longer operate), you can press the "Reset" button and the simulation will return to the starting position.

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PROCEDURE:

1) You can adjust the background shading by clicking on the "Special" button to the right and selecting "Background". Click on the "Special" button and select "Print Blank Report" to obtain a web page that can be printed and used as a lab report. (the program will not be interrupted)

2) Place the large brass weight on the balance and record its mass in your lab data sheet. In this same manner record the mass of the small brass weight and the long wooden dowel rod (boom). A hand will assist the moving of the boom.

3) Place the small wooden dowel rod in the top clamp of the metal pole (mast). Pick up the blue Newton scale and attach the top hook in the eyelet of the small dowel rod. Pick up the long string, found on a rack to the right and attach its top loop to the bottom hook of the blue scale. Note: the long and short strings must be picked up by their top loops. Drag the bottom hook of the string to the right and note its movement.

4) Pick up the boom and release it so that its left end is just to the right of the mast. Note that it clicks into place against the mast. NOW THE HARD PART: adjust the boom up and down until you can swing the bottom hook of the string over so that the loop hooks onto the end of the boom. The program will give you hints as to moving the boom up and down. When you get it right, once released the string hook will attach to the eyelet on the boom and stay in place.

5) Pick up the large brass weight and attach its hook to the end of the boom. Note that the structure is now self sustaining and the assisting hand is no longer needed. Record the force shown on the blue scale close up (in Newtons). This is the Tension force for this run.

6) Pick up the clear plastic protractor on the desk and place it on the boom so that the zero line is in the middle of the wooden rod and the right point is in the center of the eyelet. Record the angle shown (it should be somewhere between 40 and 55 degrees). This long string will have one angle and the short string another.

7) Pick up the red scale and hang it from the eyelet at the end of the boom. The blue scale will change but ignore this reading. Click on the bottom hook of the red scale, sending it into a horizontal position held by an assisting hand. Note that the blue scale returned to its original Tension value since the hand now supports its mass.

8) Gently pull the hand to the right and note the increase in force registered on the red scale. When you reach the point when the hand is pulling with the same force that the mast is pushing (T_X), the whole set-up comes apart and falls to the table. Since this is a very quick action, the program will "freeze" the value that was last shown on the red scale in a stop action view. Record this T_X value.

9) Repeat this whole procedure but this time use the small mass. Record the same data.

10) Repeat this whole procedure but this time use the short string and large mass. Record the same data.

11) Repeat this whole procedure but this time use the short string and small mass. Record the same data.

12) Calculate the requested values asked for on the lab sheet and any given by your teacher. For help on these values click on the "Special" button and select "View Data & Hints". Select "File Report" to send a copy to be viewed by your teacher.