Force Table Lab



Force Table Lab

Objective: Determine an equilibrium force using graphical, algebraic, and experimental results.

Procedure: You will be provided with 3 forces to add. I will give you the mass that will be used, and the angle at which the masses should be placed on the force table. You will determine the equilibrium force that is needed so that the center of the forces will not move.

Record the 3 masses and angles for your lab group below. (We will ignore the mass of the hanger to make the calculations easier.)

1: Mass/θ ___________________ 2: Mass/θ _____________________ 3: Mass/θ ____________________

Graphical Method:

On separate paper, graphically add the three vectors together very carefully, using the tip to tail method. Be sure to record the scale that you are using. Show all angles and mass measurements on the diagram. (Note – we are using the mass to represent the size of the force, since all the masses would just need to be scaled by gravity.)

Determine the resultant vector that would be required for the system to be in equilibrium. Draw this vector on your diagram in a different color. Measure the length of the arrow to determine the mass, and measure the angle. Show these measurements on the diagram, and record the results below.

Equilibrium vector: magnitude: _____________ direction: ____________

Algebraic Method:

On separate paper, add the vectors algebraically. Clearly show your work in calculating each of the x- and y- components. (Show the trig function that you are using, and the result.) Show your work in calculating the sum of the 3 vectors, and the angle of the sum of the three vectors.

Determine the magnitude and direction of the equilibrium vector. (This is the vector that would “cancel out” the vector that you just found through addition.) Think about the direction!

Equilibrium vector: magnitude: _____________ direction: ____________

Error:

How close are your two results? If they are very different, you must determine what went wrong before you will be allowed to complete the lab! What do you think accounts for the difference between these methods? (Don’t just say human error!)

Experimental Method:

Place the masses onto each of your hangers, to represent the 4 forces. The 4th hanger should have a total mass equal to the mass that you found using your algebraic method. You may need to use paper clips to make the masses match those from your calculations. Put the first three masses at the angles that you were given, and the 4th mass at the angle that you calculated.

Did this result angle result in equilibrium? If not, adjust the angle and/or mass of the 4th hanger until equilibrium is reached, and record the result below.

Draw a picture of your force table, showing the masses and angles of all 4 hangers, once equilibrium has been reached.

Summary:

1. What is the net force on the center ring, once equilibrium has been reached?

2. When you were finding the equilibrium vector using the graphical method, how did you know where it should go in the vector drawing?

3. When you did the algebraic method, how did you determine the direction of your equilibrium vector?

4. How close was your experimental vector to the one that you calculated algebraically? What do you think accounted for any difference?

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