PASCO ME-6807A Human Arm Model - Manual (Page 29)

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M E - 6 8 0 7 A T e a c h e r ’ s N o te s
29
Experiment 2: Biceps Force versus Weight
Typical Result:
Analysis: 1. The rela-
tionship is linear with a
slope of about 6 and a
Y-intercept of 4 N. 2. For
these typical results, accu-
rate predictions would have
been: (1) If the weight
applied to the hand is 0.98
N, the biceps force must be
about 10 N. (2) If the load
force doubles, the muscle force does not double (because of the intercept). (3) When the load force is zero, the
biceps force is 4 N. This is the force needed to support the weight of the forearm itself.
Further Analysis:
1. Free-body diagram:
2. The linear acceleration of the forearm is zero; therefore, the net force is zero. 3. The angular acceleration is
zero; therefore, the net torque is zero.
Further Study, typical results: The slope does not change significantly with different elbow angles, but
the Y-intercept does change.
force
applied by
upper arm
biceps
force
load
force
weight of
forearm