Example 8.6 A Weighted ForearmGoal Apply the equilibrium conditions to thehuman body.-HumerusProblem A W = 47.3 N (11 Ib) weight is heldin a person's hand with the forearm horizontal,as in Figure 8.11. The biceps muscle isattached d = 0.0302 m from the joint, and theweight is / = 0.351 m from the joint. Find theupward force F exerted by the biceps on theforearm (the ulna) and the downward force Rexerted by the humerus on the forearm, actingat the joint. Neglect the weight of the forearm.WBicepsUlna(a)(ь)Figure 8.11 (a) A weight held with the forearm horizontal.|(b) The mechanical model for the system.Strategy The forces acting on the forearm are equivalent to those acting on a bar of length 0.351 m, as shownin Figure 8.11b. Choose the usual x- and y-coordinates as shown and the axis O on the left end. (Thiscompletes Steps 1 and 2.) Use the conditions of equilibrium to generate equations for the unknowns, and solve.SolutionET; = TR+ TF+ TBB = 0R(0) + F(0.0302 m) - (47.3 N)(0.351 m) = 0F = 549.74Apply the second condition for equilibrium (step 3).F = 124IbEFy = F + R - 47.3 N = 0R = F - 47.3 N = 550 N - 47.3 NR = 502.44Apply the first condition for equilibrium (step 4).R = |113Ib Exercise 8.6Hints: Getting Started | I'm StuckSuppose you wanted to limit the force acting on your joint to a maximum value of8.25 x 102 N.(a) Under these circumstances, what maximum weight would you attempt to lift?Fmax(b) What force would your biceps apply while lifting this weight?Fbiceps

Given: Maximum allowed force at the joint is R = 8.25x102 N d = 0.0302 m and l = 0.351 m a) so the…

Exercise 8.6 Hints: Getting Started | I'm Stuck Suppose you wanted to limit the force acting on your joint to a maximum value of 8.25 x 102 N. (a) Under these circumstances, what maximum weight would you attempt to lift? Fmax N (b) What force would your biceps apply while lifting this weight? Fbiceps

Exercise 8.6 Hints: Getting Started | I'm Stuck Suppose you wanted to limit the force acting on your joint to a maximum value of 8.25 x 102 N. (a) Under these circumstances, what maximum weight would you attempt to lift? Fmax N (b) What force would your biceps apply while lifting this weight? Fbiceps

University Physics Volume 1

18th Edition

ISBN:9781938168277

Author:William Moebs, Samuel J. Ling, Jeff Sanny

Publisher:William Moebs, Samuel J. Ling, Jeff Sanny

Chapter12: Static Equilibrium And Elasticity

Section: Chapter Questions

Problem 39P: The forearm shown below is positioned at an angle with respect to the upper arm , and a 5.0- kg...

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