Resultant of Forces Lab Honors
Name: ___________________
Partners: _________________
Purpose:
Equipment:
Procedure:
Force Board
1.
Use a Force Board to produce 3 different forces of at least 9 Newtons or 900 grams, depending on which
board you use, each going three different directions. Make sure the center ring is close to the center of the
Force Board.
2.
Place a piece of paper under the strings and scales in the center of the board and carefully mark the point of
intersection of the forces (the center of the ring) and the direction each force acts.
3.
Record the magnitude of each force and label them A, B, and C. A and B will represent 2 forces acting at a
point, and C then will be the force needed to balance the other two and produce equilibrium (the
equilibrant).
4.
Remove the paper from the force board.
Hanging Animal
5.
Choose one of the hanging stuffed animals. Record the magnitude of each known force (in Newtons) from
the spring scales as well as the angle between each pair of the three strings. Make sure the angles add up to
3600.5 degrees.
6.
Label the two upward vectors A and B, and the string supporting the animal should be labeled C.
Head-to-Tail Method – Graphically
7.
Pick the data from either the force board or the hanging animal. On a plain piece of paper, choose an
appropriate scale and draw A, B, and C as vectors. Label each vector with its magnitude (for the stuffed
animals, C is unknown). Make sure that the angles between the vectors are accurate. Make sure they add up
to 3600.5 degrees.
8.
Graphically add vectors A and B to determine the magnitude and direction of the resultant. Draw this
solution on your diagram, measure it and determine its magnitude and direction. Label this resultant C'.
Head-to-Tail Method – Mathematically
9.
Use the Law of Cosines to mathematically calculate the magnitude of C' from the previous part and compare
this to your graphical result. Use the Law of Sines to calculate the direction of the resultant. Do these
calculations on your vector diagram.
Law of Cosines
C 2  A 2  B 2  2 * A * B * cos 
Law of Sines
sin  A sin  B sin  C


A
B
C
B
c
A
B
Component Method - Graphically
A
C
10. Using the other set of data, draw vectors A, B and C onto graph paper and resolve the vectors into x and y
components.
11. Again add A and B producing C' graphically by components (add the x & y components graphically and
then find the size and direction of resultant).
Component Method - Mathematically
12. Add A and B producing C' mathematically by the component methods (find individual x and y components
using sine and cosine functions, add x and y components separately, create a new right triangle with the new
x and y components, and find the size and direction of the resultant, C').
Questions, Analysis & Conclusions: (remember to cite values from your data to support your
claims!)
1.
Discuss what your results show about the sizes and directions of C and C' for both trials. Be specific in
telling what results you got.
2.
What conclusions can you make about the two different methods of adding vectors together, head-to-tail vs.
component method?
3.
What can you conclude about graphical vs. mathematical results?
In your lab report be sure to include vector diagrams including calculations, scale used, and indicate
which equipment was used for each trial.