Phy 231
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: **
Part 1 REVISED
** 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: **
0, 7, 14
7.2, 7, 7
0.18, 0.175, 0.175
Point B was measured as the reference point.
The Newtons were obtained by looking at previous experiments as a reference and using a ratio to come up with the correct force.
The results are the positions of the vertical lines, the lengths of the rubber bands, and their respective forces. They were found by setting up the system described above and making the necessary measurements.
** Net force and net force as a percent of the sum of the magnitudes of all forces: **
-7.2
34%
The net force was obtained by adding the force vectors. The percentage is the net force as a percentage of the total force.
** Moment arms for rubber band systems B and C **
11cm, 12cm
The moment arc is the distance from the fulcrum to the end of the rubber band at each point.
** Lengths in cm of force vectors in 4 cm to 1 N scale drawing, distances from the fulcrum to points B and C. **
0.72, 0.7, 0.7
11, 12
The length of the vectors were found by multiplying the forces found above by 4. The distances from the fulcrum were found by measuring the drawings of the system.
** Torque produced by B, torque produced by C: **
-1.925, +2.1
If counterclockwise is positive, then C's torque would be positive, while B's torque would be negative. They were obtained by multiplying the moment-arc by the force.
** Net torque, net torque as percent of the sum of the magnitudes of the torques: **
.175
4.3%
The net torque was found by adding the two torque vectors together. This was then divided by the sum of the absolute value of the torque vectors to give you the percentage.
** 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? **
30 min revision
** Optional additional comments and/or questions: **
I'm still not sure about those forces, but given the forces you inferred your analysis is OK.
Phy 231
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: **
Part 2
** 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: **
** Net force and net force as a percent of the sum of the magnitudes of all forces: **
** Moment arms for rubber band systems B and C **
** Lengths in cm of force vectors in 4 cm to 1 N scale drawing, distances from the fulcrum to points B and C. **
** 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: **
1.2N, 8cm, 9.6 N*cm
1.5N, 8.2cm, 12.3 N*cm
.76N, 7.6cm, 5.78 N*cm
1N, 7.8cm, 7.8 N*cm
** 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: **
-.06
The picture of my bridge system has two vertical forces upwards with a total of 2.2 N and two vertical forces downwards with a total of 2.26 N. I guess it 'fails' to depict all the forces because it does not take into account the weight of the horizontal rod.
** Net torque for given picture; your discussion of whether this figure could be accurate for a stationary rod: **
-0.68
This picture is not an accurate depiction of forces since it is a picture of the force vectors. This does not tell the whole story of torque because force is only one component of torque. The other component, moment-arc, is not shown in the picture and so does not accurately tell of the torque.
** 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: **
9.6 N*cm
1.2 N, -.06
1.3%
-.68, 35.48, 2%
The first lines of results are the magnitude of the force as well as the percent of the magnitude as part of the sum of the total force. The lower lines are the same for the torque. The magnitude and percent of the total torque.
** 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: **
11.48 N*cm
0.2N, 5N
4%
1.76, 40.4, 4.4%
The first line contains the torque for the force at point A. The second line consists of hte magnitude of the force and the sum of the forces. The third line is the percent of the magnitude compared to the sum. The fourth line is the same information but with the torques.
** In the second setup, were the forces all parallel to one another? **
The forces were mostly parallel to each other. I would say there was a deviation in about +- 5 degrees. These estimates were made by holding a 90 degree angle up to the lines drawn of the system.
** Estimated angles of the four forces; short discussion of accuracy of estimates. **
85, 87, 87, 90
These estimates were made just by eyeballing the drawing of the system. They didn't deviate much from the 90 degree angle so it was relatively easy to estimate.
** 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? **
45 min
** Optional additional comments and/or questions: **
This looks good.
&#Let me know if you have questions. &#