Question

६८-

The diagram above shows a side view of a person’s arm. The forearm and hand together weigh 19N (W_FH = 19N). The center of gravity at point T is located 24cm from the elbow joint. The person is holding a bowling ball 38cm from the elbow and the ball weighs 47N (W_B = 47N).

(a) Calculate the torque produced by the weight of the forearm and hand about the elbow joint. Include the direction of the torque.

(b) Calculate the torque that the bowling ball produces about the elbow joint. Include the direction of the torque.

(c) How much torque would the biceps brachii need to produce to maintain this position in static equilibrium? (Assume that this is the only active elbow flexor at this time). Include the direction of the torque.

(d) If the biceps brachii attaches 4.3cm from the elbow joint at an angle α = 30°, what is the moment arm for this force?

(e) If the biceps brachii attaches 4.3cm from the elbow joint at an angle α = 30°, what is the moment arm for this force?

Answer 1

Yf sino ca) Pue 0-24X 19x Singo' 456 Nm clockloise ) 0 38 X47 SingD' clock oire 7.86 Nm Torqu equined to keep am net torqu by arm and equil brium weignt C,C4.S6 19.86= 22.42N But ths tim ts should e anticlockois (X dsino MoMent arm 43 Sin 30 4.3 2 1S cm A ameQueston as