torques

Your work on torques 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:

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:

3.5, 10.3, 14.3

7.8, 8.4, 9.2

.2, .7, 1.3

The reference point that was used to measure the others was 3.5 cm to the left of the left most point.

I used the lenghts of the rubberbands to find the forces.

Net force and net force as a percent of the sum of the magnitudes of all forces:

-2

100

I believe you have .2 N and 1.3 N downward, and two .7 N upward forces, which give you a net force of -.2 N + 2 * .7 N - 1.3 N = .1 N, which is upward.

Moment arms for rubber band systems A and C

6.8, 4.2

Both moment arms have to be with respect to the same point. I don't think the moment arms for A and C could be 6.8 cm and 4.2 cm. The 6.8 cm looks right for the moment of A relative to B, but 4.2 cm is not the moment of C relative to B.

Lengths in cm of force vectors in 4 cm to 1 N scale drawing, distances from the fulcrum to points B and C.

.2, 3.5, 4.4

3.9, 8.8

Torque produced by B, torque produced by C:

+.04, -5.72

Net torque, net torque as percent of the sum of the magnitudes of the torques:

-5.68

284%

Since the sum of the magnitudes was -2, -5.68/-2, thus giving you a percent of 284.

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):