Your 'torques' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** Your optional message or comment: **
really confused here, could you check my work so far and make some corrections?
** Positions of the three points of application, lengths of systems B, A and C (left to right), the forces in Newtons exerted by those systems, description of the reference point: **
LINE 1
1.25, 7.75, 11
LINE 2
length of rubberbands
B 8.4 cm
A 7.9 cm
C 9.1 cm
LINE 3
forces
B 1.0 N
A .19 N
C 2.0 N
LINE 4
What I did was I drew the rod exactly according to scale, which was 15.5 cm. I placed the B rubberband system at 1.25 cm from the edge on the left. The A system was located in the middle which was at 7.75 cm. System C was located 3.25 cm beyond the A system, @ 10.55 cm.
LINE 5
to obtain the Forces in Newtons I used the information gathered in my cm v. Force calibration curve that I constructed on July 12 for the rubberband calibration experiment.
LINE 6
To obtain my results I measured the distances and then converted them to Newtons for my experiment.
I then checked my work using the formula force * distance = force * distance.
For this formula to work there has to be a mid point, kind of like a seesaw and then weights distrubuted on each side of the rod.
So to check my work I used the equation
f1*d1=f2*d2
1 N * 6.5 cm = 2 N * 3.25 cm
6.5 N * cm = 6.5 N * cm
** Net force and net force as a percent of the sum of the magnitudes of all forces: **
Fnet = Force in A + B + C
.19 N + 1 N + 2 N = 3.19 N
The force exerted at A is upward, the other forces are downward. You need to use + and - signs as appropriate.
There are two rubber bands at A. Also note that these rubber bands are almost certainly exerting more force than you report, though the forces you report do seem to agree with the calibrations.
3.19 N / ( ( 8.4 cm * 1 N ) + ( 7.9 cm * .19 N ) ( 9.1 cm * 2 N ) )
3.19 N / 28.101 cm * N
0.114 cm
** Moment arms for rubber band systems B and C **
Moment-arm for the system B
distance from A to B on rod = 6.5 cm
distance from top of point B to bottom = 8.4 cm
6.5 ^ 2 + 8.4 ^ 2 = 10.61 cm
The moment arm is the displacement from axis to the point where the line of the force crosses the axis. Since the forces are perpendicular to the rod, the moment arms are equal to the displacement from axis to the point of application.
In this case the magnitudes of the moment arms are just 6.5 cm and 3.25 cm.
Moment-arm for the system C
distance from A to C on rod = 3.25 cm
distance from top of point C to bottom = 9.1 cm
3.25 ^ 2 + 9.1 ^ 2 = 9.7 cm
** Lengths in cm of force vectors in 4 cm to 1 N scale drawing, distances from the fulcrum to points B and C. **
if 4 cm = 1 N then
B = 8.4 cm = 2.10 N ( down )
A = 7.9 cm = 1.98 N ( up )
C = 9.1 cm = 2.28 N ( down )
From A to B = 6.5 cm
6.5^2 + 8.4 ^ 2 = 10.6
From A to C = 3.25 cm
9.1 ^2 + 3.25 ^ 2 = 9.7
** Torque produced by B, torque produced by C: **
** Net torque, net torque as percent of the sum of the magnitudes of the torques: **
** Forces, distances from equilibrium and torques exerted by A, B, C, D: **
** The sum of the vertical forces on the rod, and your discussion of the extent to which your picture fails to accurately describe the forces: **
** Net torque for given picture; your discussion of whether this figure could be accurate for a stationary rod: **
** For first setup: Sum of torques for your setup; magnitude of resultant and sum of magnitudes of forces; magnitude of resultant as percent of sum of magnitudes of forces; magnitude of resultant torque, sum of magnitudes of torques, magnitude of resultant torque as percent of the sum of the magnitudes: **
** For second setup: Sum of torques for your setup; magnitude of resultant and sum of magnitudes of forces; magnitude of resultant as percent of sum of magnitudes of forces; magnitude of resultant torque, sum of magnitudes of torques, magnitude of resultant torque as percent of the sum of the magnitudes: **
** In the second setup, were the forces all parallel to one another? **
** Estimated angles of the four forces; short discussion of accuracy of estimates. **
** x and y coordinates of both ends of each rubber band, in cm **
** Lengths and forces exerted systems B, A and C:. **
** Sines and cosines of systems B, A and C: **
** Magnitude, angle with horizontal and angle in the plane for each force: **
** x and y components of sketch, x and y components of force from sketch components, x and y components from magnitude, sine and cosine (lines in order B, A, C): **
** Sum of x components, ideal sum, how close are you to the ideal; then the same for y components. **
** Distance of the point of action from that of the leftmost force, component perpendicular to the rod, and torque for each force: **
** Sum of torques, ideal sum, how close are you to the ideal. **
** How long did it take you to complete this experiment? **
2 hours so far
** Optional additional comments and/or questions: **
Most of what you have looks good. However see my notes about signs, etc.. You should still have your paper, so be sure to double-check the measurement of the length of the rubber band system at A and the force exerted at that point, but that's not a big deal.