The figure below shows a human arm that weighs 43.40 N. The arm is extended outward and is motionless. The gravitational force F, on the arm acts at point A, a distance of 0.2900 m from the shoulder joint, which is represented by point O. The shoulder pushes down and to the right on the humerus bone of the arm with a force F, at point O, at an angle e as shown. The deltoid muscle pulls back on the arm toward the shoulder with tension force F. This tension force acts at a point 0.08000 m to the right of point o, and it is directed up and to the left, at a 12.00° angle with respect to the horizontal.

A man holds a 153-N ball in his hand, with the forearm horizontal (see the figure). He can support the ball in this position because of the flexor muscle force , which is applied perpendicular to the forearm. The forearm weighs 18.6 N and has a center of gravity as indicated. Find (a) the magnitude of  and the (b) magnitude and (c) direction (as a positive angle counterclockwise from horizontal) of the force applied by the upper arm bone to the forearm at the elbow joint.

1. The picture shows a heavy ball held in the palm of a hand. The mass of the ball M is 7.5 kg. The lower arm is horizontal and is held by the force from the bicep Biceps muscle in the vertical upper arm. Given that the mass of the lower arm is 2.0 kg, what is the magnitude of (a) the force of the biceps muscle on the lower arm and (b) the force between the bony structures at the elbow Elbow contact contact point? point 4.0 cm Lower arm (forearm plus hand) center 15 cm Draw a free body diagram to indicate all the forces on the lower arm. And write down where is the pivot -33 cm of mass point when you calculate the torque in each part.

Question 4. A rod is lying on the top of a table. One end of the rod is hinged to the table so that the rod can rotate freely on the table top. Two forces, both parallel to the table top, act on the rod at the same place. One force is directed perpendicular to the rod and has a magnitude of 31 N. The second force has a magnitude of 52 N and is directed at an angle with respect to the rod. If the sum of the torques due to the two forces is zero, what must be the angle? Ans: 36.59°

A diver of weight 510 N stands at the end of a diving board of length L = 4.9 m and negligible mass (the figure). The board is fixed to two pedestals separated by distance d = 2.0 m. Take the upward direction to be positive. Of the forces acting on the board, what are (a) the force from the left pedestal and (b) the force from the right pedestal? L (a) Number Units (b) Number Units

When a gymnast weighing 740 N executes the iron cross as in figure (a), the primary muscles involved in supporting this position are the latissimus dorsi ("lats") and the pectoralis major ("pecs"). The rings exert an upward force on the arms and support the weight of the gymnast. The force exerted by the shoulder joint on the arm is labeled F while the two muscles exert a total force F on the arm. Determine the magnitude of the force F Note that one ring supports half the weight of the gymnast, which is w 370 N as indicated in figure (b). Assume that the force F acts at an angle of 45° below the horizontal at a distance of 4.0 cm from the shoulder joint. In your estimate, take the distance from the shoulder joint to the hand to be L = 75 cm and ignore the weight of the arm. m kN Shoulder joint 4.0 cm- 45.00 Ed Bock/CORBIS

When a person stands on tiptoe (a strenuous position), the position of the foot is as shown in Figure a. The total gravitational force on the body, F, is supported by the force g' n exerted by the floor on the toes of one foot. A mechanical model of the situation is shown in Figure b, where T is the force exerted by the Achilles tendon on the foot and R is the force exerted by the tibia on the foot. Find the values of T, R, and 0 when F = n = 780 N. (For 0, enter the smaller of the two possible values between 0° and 90°.) -Achilles tendon Tibia 15.0° 18.0 cm 25.0 cm b T = R =

A man holds a 186-N ball in his hand, with the forearm horizontal (see the figure). He can support the ball in this position because of the flexor muscle force M, which is applied perpendicular to the forearm. The forearm weighs 21.6 N and has a center of gravity as indicated. Find (a) the magnitude of M and the (b) magnitude and (c) direction (as a positive angle counterclockwise from horizontal) of the force applied by the upper arm bone to the forearm at the elbow joint. (a) Number (b) Number i (c) Number i Upper arm bone- Elbow joint 0.0510 m+ Units Units Units Flexor muscle M -0.0890 m -0.330 m-

A beam resting on two pivots has a length of L = 6.00 m and mass M = 79.0 kg. The pivot under the left end exerts a normal force n, on the beam, and the second pivot placed a distance l = 4.00 m from the left end exerts a normal force n,. A woman of mass m = 59.5 kg steps onto the left end of the beam and begins walking to the right as in the figure below. The goal is to find the woman's position when the beam begins to tip. M (a) Sketch a free-body diagram, labeling the gravitational and normal forces acting on the beam and placing the woman x meters to the right of the first pivot, which is the origin. (Submit a file with a maximum size of 1 MB.) Choose File No file chosen This answer has not been graded yet. (b) Where is the woman when the normal force n, is the greatest? X = (c) What is n, when the beam is about to tip? N (d) Use the force equation of equilibrium to find the value of n, when the beam is about to tip. N (e) Using the result of part (c) and the torque equilibrium…

DA man holds a 178-N ball in his hand, with the arm bone- 22. Upper - rlexor muscle forcarm horizontal (sce the draw- ing). He can support the ball in this position because of the flexor muscle force M, which is applied perpendicular to the forearm. The forearm weighs 22.0 N and has a center of gravity as indicated. Find (a) the magnitude of M and (b) the magnitude and direction of the force applied by the upper arm bone to the forearm at the elbow joint. Elbow cg joint '0.0890 m -0.330 m- 0.0510 m