Real-world application. Equipment: a barbell (above 10 lbs) or a heavy book, a meter stick or another length measuring instrument. Lift the barbell by doing a bicep curl. Watch the change of Upper Biceps arm Barbell the shape of your bicep. What is the role of the bicep in lifting the barbell? Where is it attached to the arm? Consider the axis of rotation to be in the 4.0 cm elbow joint. How far away is the barbell from the 40 cm axis of rotation? How far is the bicep from the axis of rotation? Estimate the force that the biceps muscle exerts on the forearm holding the barbell. What assumptions did you make in working the problem?

None

Many aspects of a gymnast's motion can be modeled by representing the gymnast by four segments consisting of arms, torso (including the head), thighs, and lower legs, as in the figure below. Thigh O Arm Leg 60° 60° Torso a (i In the figure, (b) shows arows of lengths re locating the center of gravity of each segment. Use the data below and the coordinate system shown in figure (b) to locate the center of gravity of the gymnast shown in figure (a). Masses for the arms, thighs, and legs include both appendages. (Enter your answers in m, to at least three significant figures.) Segment Mass (kg) Length (m) rcg (m) Arms 6.81 0.548 0.236 Torso 33.6 0.613 0.337 Thighs 14.1 0.368 0.149 Legs 7.50 0.350 0.227 HINT Xcg 0.458 %D Y cg 0.0949 X m

Inigo and Fezzik push with perpendicular forces on a heavy door with width R. Inigo pushes with force F at 3R/4 from the hinge, while Fezzik pushes with force 2F at R/3 from the hinge. Which of the following descriptions is correct? (diagram shows the top-down view) hinge O B ОА A. Inigo (pushing with F) exerts a greater a torque on the door. B. Fezzik (pushing with 2F) exerts a greater a torque on the door. C. The torques they exert are equal in magnitude. D. There is zero net torque on the door. OD 3R/4 O C R/3 2F

1. The figure below shows the normal configuration of the head with proper posture. The center of mass for the weight of the skull is labeled W and the muscles that attach to the back of the skull are labeled M. Assume all quantities are correct to 2 significant figures. M W a) Determine the mechanical advantage of the skull muscles when d₁ 20 mm and d₂ = 26 mm. Hint: Which force on the fulcrum (rotation point) is the effort, and which is the load? Enter to 2 significant figures Mechanical Advantage: b) Improper posture and positioning of the head can lead to muscle tension headaches. If the head begins to shift forward while studying or reading, the center of mass moves further from the fulcrum or pivot point. It is a subtle change, but the figure below shows the head shifted forward. The center of mass for the weight of the skull is labeled W and the muscles that attach to the back of the skull are labeled M. Determine the new mechanical advantage of the skull muscles when d₁ = 16 mm…

Calculate the shear force acting on the lumbar vertebra.  calculate the compressive force acting on the lumbar vertebra The GRF is 225 N. The GRF has a moment arm of 0.40 m relative to the vertebra axis of rotation. The weight of the trunk is 350 N. Wtrunk has a moment arm of 0.3 m relative to the vertebra axis of rotation. Fm is 300 N. Fm has a moment arm of 0.05 m relative to the vertebra axis of rotation.