Kinesiology 2241A/B Lecture Notes - Lecture 10: Shoulder Joint, Motive Studios, Resultant Force

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aquamarinefish391

5 Nov 2015

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4 functions of muscles: balance 2 or more forces, force advantage, linear rom and/or speed, change direction of f motive. Example: throw a ball 2 different ways lever: help with force & accuracy: wheel axle: higher end point velocity (i. e. overarm throw pattern) axle: upper arm (rotating about longitudinal axis) wheel: lower arm. Properties of a force: magnitude, direction, point of application, line of action. Cg of forearm is co-linear with axis of rotation (not through axis) = no torque resultant motion in the direction of the greatest torque. Weight of arm + weight of case = large. : action line of gravity acting through lower arms cg to axis of rotation. : action line of muscle pulling on bone to axis rotation (elbow joint) 4. 4a: tmotive = tresistive no motion. Resultant comprised of 2 components: ro = vertical/perpendicular component, stabl/ disl = horizontal/parallel component. Muscle pulls on bone at specific angle: <90 .

Related Questions

Answer the correct answer with t or f

1.)In a first class lever, the effort and load are on oppositesides of the fulcrum
(true or false)

2.)A lever is in static balance if forces on it are equal inmagnitude and opposite in direction(true or false)

3.)The effort torque is equal length of the load arm multiplied bythe effort force.
(true or false)

4.)IMA is always equal to AMA (true or false)

5.)If the effort arm is increased enough, the efficiency of thelever will exceed 100%
(true or false)

6.)A can opener is a simple machine using a wheel and axle. (trueor false)

7.)A bicycle is a compound machine using levers and gears. (true orfalse)

1. A physical therapy patient contracts her biceps muscle, andexerts a horizontal force of 180 N on the spring shown in thefigure at right. Assume the forearm rotates at the elbow. a) Drawan extended force diagram of the forearm (everything from the elbowto the tip of the fingers) showing the pivot point and all of theforces acting on the forearm where they actually are applied. Youwonât know the magnitudes (or even the directions) of these forcesuntil you finish the whole problem but just draw reasonable vectorsfor now.
b) Now draw a force diagram with the forearm as a dot. c) Use thefact that the forearm is perfectly stationary at all times to findthe horizontal force that her biceps exerts on her forearm AND theforce exerted by the bone of the upper arm (shown below the biceps)on the forearm (weight = 30N). Note that muscles can only PULL inthe direction along the muscle, but that ligaments (like the onesin the elbow that connect the upper arm with the forearm) can exertforces in any direction. d) Briefly explain in complete Englishsentences (i.e., not just equations) why the bone of the upper armexerts such a large force on the forearm. e) What is the advantageof having the point where the biceps is attached to the forearm soclose to the elbow? What is the disadvantage of having it attachedso close?

2. You are trying to roll your bicycle wheel (of mass m andradius R) over a curb (of height h). To do this, you apply ahorizontal force F in the direction of desired motion. What is theminimum magnitude of the force that will successfully raise thewheel onto the curb when the force is applied (a) at the center ofthe wheel, and (b) at the top of the wheel? (c) In which case isthe magnitude of the force the least?

3. A hay bale is being dragged along a horizontal surface withconstant speed by a force F. The hay bale is 0.6 m high, 0.3m wide,and 0.9 m long (the side the force is applied to, perpendicular tothe direction of motion). The coefficient of kinetic friction is0.33. (a) Find the magnitude of the force, F. (b) Find the height,h, at which the bale will begin to tip over if the force is appliedat that height.

Kinesiology 2241A/B Lecture Notes - Lecture 10: Shoulder Joint, Motive Studios, Resultant Force

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