Physics for Scientists and Engineers: Foundations and Connections
1st Edition
ISBN: 9781133939146
Author: Katz, Debora M.
Publisher: Cengage Learning
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Chapter 12.5, Problem 12.6CE
For each exercise shown in Figure 12.22, how does the moment arm on the dumbbell compare to the length of the person’s arm?
FIGURE 12.22
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Cole is trying a biceps curl and attempting to lift a 150 N dumbbell. The moment arm of this weight about his elbow joint is 25 cm. The force created by the elbow flexor muscles is 2000 N. The moment arm of the elbow flexor muscles is 2 cm. Is Cole able to lift the weight with this amount of force in his flexor muscles?
John is performing an isometric contraction of the quadriceps to hold a 500 N weight at an angle of 45° of knee extension (i.e., 45° below the horizontal). Assume the length of the lower leg is 42.5 cm. How much force must the quadriceps produce if the moment arm for the patellar tendon is 10 mm?
A model of the forearm. The main bone of the forearm is connected to the arm bone through the elbow joint.Two muscles, the triceps and the biceps, are attached to this bone, on either side of the joint. The diagram below represents feel a pattern of the forearm. The bones and the flesh of the forearms, including the hand, are represented by a rod homogeneous of 1,5 kg having a length of 40,1 cm. The articulation is a pivot attached to the vertical arm bone (considered fixed). As a muscle can only pull, never push, the triceps and biceps are represented by strings: the triceps is fixed at the end left of the forearm, 0,9 cm from the pivot; the bicep is attached to 3,5 cm to the right of the pivot.
(a) In this situation, which muscle allows the forearm to remain in balance? What is the modulates the tension in this muscle?
(b) We add a block of 3,6 kg on the hand, 35,1 cm from the elbow joint; if the forearm remains horizontal, which becomes the module of the voltage calculated in (a)?
Chapter 12 Solutions
Physics for Scientists and Engineers: Foundations and Connections
Ch. 12.1 - Figure 12.5 shows two rotating objects. Indicate...Ch. 12.2 - Prob. 12.2CECh. 12.2 - Prob. 12.3CECh. 12.2 - Prob. 12.4CECh. 12.2 - Prob. 12.5CECh. 12.5 - For each exercise shown in Figure 12.22, how does...Ch. 12 - Often, we model the Moon as a particle in a...Ch. 12 - Suppose a satellite orbits the Earth such that it...Ch. 12 - Prob. 3PQCh. 12 - Prob. 4PQ
Ch. 12 - A ceiling fan is rotating counterclockwise with a...Ch. 12 - As seen from above the Earths North Pole, the...Ch. 12 - A rotating objects angular position is given by...Ch. 12 - A rotating objects angular position is given by...Ch. 12 - Jupiter rotates about its axis once every 9 hours...Ch. 12 - Prob. 10PQCh. 12 - Prob. 11PQCh. 12 - Prob. 12PQCh. 12 - Prob. 13PQCh. 12 - Prob. 14PQCh. 12 - Prob. 15PQCh. 12 - A disk rolls up an inclined plane as shown in...Ch. 12 - Jeff, running outside to play, pushes on a...Ch. 12 - A potters wheel rotating at 240 rev/min is...Ch. 12 - Friction in an old clock causes it to lose 1...Ch. 12 - A wheel starts from rest and in 12.65 s is...Ch. 12 - Prob. 21PQCh. 12 - Starting from rest, a wheel reaches an angular...Ch. 12 - A potters wheel is rotating with an angular...Ch. 12 - The angular speed of a wheel is given by (t) =...Ch. 12 - Prob. 25PQCh. 12 - Prob. 26PQCh. 12 - An electric food processor comes with many...Ch. 12 - Prob. 28PQCh. 12 - A bicyclist is testing a new racing bike on a...Ch. 12 - Prob. 30PQCh. 12 - A disk is initially at rest. A penny is placed on...Ch. 12 - Prob. 32PQCh. 12 - Consider again the two wind turbines in Problem...Ch. 12 - Consider again the two wind turbines in Problem...Ch. 12 - In testing an automobile tire for proper...Ch. 12 - Prob. 36PQCh. 12 - A merry-go-round at a childrens park begins at...Ch. 12 - A wheel rotating at a constant rate of 1850...Ch. 12 - Why are doorknobs placed on the edge opposite the...Ch. 12 - Prob. 40PQCh. 12 - Prob. 41PQCh. 12 - Prob. 42PQCh. 12 - A wheel of inner radius r1 = 15.0 cm and outer...Ch. 12 - A uniform plank 6.0 m long rests on two supports,...Ch. 12 - Prob. 45PQCh. 12 - Prob. 46PQCh. 12 - Prob. 47PQCh. 12 - Prob. 48PQCh. 12 - Prob. 49PQCh. 12 - Prob. 50PQCh. 12 - Prob. 51PQCh. 12 - Given a vector A=4.5+4.5j and a vector B=4.5+4.5j,...Ch. 12 - A square plate with sides 2.0 m in length can...Ch. 12 - Prob. 54PQCh. 12 - A disk with a radius of 4.5 m has a 100-N force...Ch. 12 - Disc jockeys (DJs) use a turntable in applying...Ch. 12 - Prob. 57PQCh. 12 - Prob. 58PQCh. 12 - A wheel initially rotating at 85.0 rev/min...Ch. 12 - Prob. 60PQCh. 12 - A centrifuge used for training astronauts rotating...Ch. 12 - Problems 62 and 63 are paired. 62. C A disk is...Ch. 12 - Prob. 63PQCh. 12 - A potters wheel rotates with an angular...Ch. 12 - Prob. 65PQCh. 12 - Prob. 66PQCh. 12 - Prob. 67PQCh. 12 - Lara is running just outside the circumference of...Ch. 12 - The propeller of an aircraft accelerates from rest...Ch. 12 - A ball rolls to the left along a horizontal...Ch. 12 - Three forces are exerted on the disk shown in...Ch. 12 - Consider the disk in Problem 71. The disks outer...Ch. 12 - Prob. 73PQCh. 12 - Prob. 74PQCh. 12 - Prob. 75PQCh. 12 - Prob. 76PQCh. 12 - Prob. 77PQCh. 12 - Prob. 78PQCh. 12 - Prob. 79PQCh. 12 - Prob. 80PQCh. 12 - If the rod in Problem 79 is in equilibrium, what...Ch. 12 - As a compact disc (CD) spins clockwise as seen...Ch. 12 - A disk-shaped machine part has a diameter of 40.0...Ch. 12 - Prob. 84PQ
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- What is the force that the biceps should exercise when a 45 N-weight ball is held in the hand with the Horizontal forearm as in the figure. The biceps connect with the forearm by a tendon attached 5 cm from the The elbow articulation. Suppose the weight of the forearm and hand together is 13.5 N. You must give your answer with a Decimalarrow_forwardScientists have studied how snakes grip and climb ropes. In one study, they found that an important characteristic of a rope is its "compliance"--that is, how easily the rope, while under tension, can be flexed. (Figure 1) shows how scientists measured a rope's compliance by attaching it to two strings, each supporting an identical mass mm. The lower part of the rope is held under tension by a spring (not shown). The strings contort the rope so that its middle section lies at angle θ. For θ = 45∘ and mm = 400 g, what is the tension T2 in the middle part of the rope?arrow_forwardIn the figure below, the CG of the pole held by the pole vaulter is 2.04 m from the left hand, and the hands are 0.713 m apart. (Assume the vaulting pole has a mass of 2.52 kg.) Calculate the force (in N) exerted by his right hand. (Enter the magnitude.)arrow_forward
- You hold a 1.80-N softball in your hand as shown in the figure. Consider your forearm and hand to be a uniform rod with a mass of 1.65 kg and the distance between the elbow joint and the ball in your hand is 2L = 22.0 cm. Your biceps exerts an upward force of 13.5 N on the forearm and is attached at a distance of d = 2.20 cm from the elbow. Bicеps Mg (a) Using the elbow joint as the axis of rotation, determine the magnitude of the net torque acting about the elbow due to the forearm, hand, and ball. N- m (b) In which direction will the forearm and hand rotate, if the net torque obtained in part (a) is nonzero? O counterclockwise O no rotation O clockwisearrow_forwardThe arm shown in the figure supports a 4kg sphere. The mass of the hand and forearm together is 3kg and its weight acts at a point 15 cm from the elbow. Determine the force exerted by the biceps muscle.arrow_forwardExplain how dumbbell curls (flexing the elbow while holding dumbbells) with (A) the forearms supinated and (B) the forearms pronated signifncalty alter the demands placed on the elbow flexors. Mention the muscles involved in your answer. Edit View Insert Format Tools Table 12pt v Paragraph v |BIU A ev T? v :arrow_forward
- Scientists have studied how snakes grip and climb ropes. In one study, they found that an important characteristic of a rope is its "compliance"--that is, how easily the rope, while under tension, can be flexed. (Figure 1) shows how scientists measured a rope's compliance by attaching it to two strings, each supporting an identical mass m. The lower part of the rope is held under tension by a spring (not shown). The strings contort the rope so that its middle section lies at angle θ. . a)For θ = 45 ∘ and m = 300 g, what is the tension T1 in the upper part of the rope? For θ = 45 ∘ and m = 300 g, what is the tension T2 in the middle part of the rope?)arrow_forwardWhy does the torque producing capabilities of the triceps increase at full elbow extension (remember T=Fxd)?arrow_forwardMy book has the answers as a) 10N b) 196N But I can't figure out the proper way to work it out. I figured you start by using torque and the weight of the board plus the forces of each support to make a equation for Fn1. Then once you solve for it go back and make a equation for Fn2. But I'm not getting the answers in my book when I do this.arrow_forward
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