Explanation Given data: Refer to the FIGURE P8.63 in the textbook for the standing position of the woman and its measurements. Mass of the woman ( m ) is 60 kg. Angle made by the sole of the woman with the floor ( θ ) is 25 ° . From the Figure, the distance between the Achilles tendon to toe ( d Ach-toe ) is 20 cm and the distance between the Ankle pivot to the toe ( d Ank-toe ) is 15 cm. Length of the Achilles tendon ( L ) is 15 cm. Cross-sectional area of Achilles tendon ( A ) is 110 mm 2 . Formula used: Write the expression for force exerted by the Achilles tendon as follows. F Ach = Y A L Δ L (1) Here, Y is the Young’s modulus, A is the cross-sectional area of the Achilles tendon, L is the length of the Achilles tendon, and Δ L is the change in length of the Achilles tendon (stretching length). Write the expression for weight of the object as follows. w = m g (2) Here, m is the mass of the object, and g is the acceleration due to gravity, which is 9.8 m s 2 . Write the expression for static equilibrium condition of the torque as follows. ∑ τ = 0 (3) Here, ∑ τ is the sum of the torques acting on the object. Write the expression for torque in terms of force and distance as follows. τ = F d (4) Here, F is the force, and d is the distance. Consider each foot of the woman supports half her weight. From the given data, the weight of each foot of the woman is half of the weight of the woman. Therefore, write the expression for weight of one foot of the woman as follows. w F = 1 2 ( w ) (5) Here, w is the weight of the woman. Calculation of weight of the woman: Substitute 60 kg for m , and 9.8 m s 2 for g in equation (2), w = ( 60 kg ) ( 9.8 m s 2 ) = 588 kg ⋅ m s 2 = 588 N { ∵ 1 kg ⋅ m s 2 = 1 N } Calculation of weight of one foot: Substitute 588 N for w in equation (5). w F = 1 2 ( 588 N ) = 294 N Compute the torques around the Ankle pivot by modify the expression in equation (3), by using the equation (4) as follows. F Ach d Ach-Ank + ( − w F ) d Ank-toe = 0 (6) Here, F Ach is the force exerted by the Achilles tendon the heel of the foot of the woman, d Ach-Ank is the distance between the Achilles tendon and the Ankle pivot, which is 5 cm form the Figure P8

College Physics: A Strategic Approach (3rd Edition)

3rd Edition

ISBN: 9780321879721

Author: Randall D. Knight (Professor Emeritus), Brian Jones, Stuart Field

Publisher: PEARSON

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Center of Gravity of a system

The centre of gravity is a property that is based on the geometry of a rigid body or any particle. It is described as an equilibrium point or a hypothetical location where the total weight of the body is concentrated.

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Chapter 8, Problem 65MSPP

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Chapter 8, Problem 64MSPP

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Chapter 8 Solutions

College Physics: A Strategic Approach (3rd Edition)

Ch. 8 - An object is acted upon by two (and only two)...Ch. 8 - Prob. 2CQ Ch. 8 - Could a ladder on a level floor lean against a...Ch. 8 - If you are using a rope to raise a tall mast,...Ch. 8 - Prob. 5CQ Ch. 8 - Prob. 6CQ Ch. 8 - Prob. 7CQ Ch. 8 - A spring exerts a 10 N force after being stretched...Ch. 8 - The left end of a spring is attached to a wall....Ch. 8 - A spring is attached to the floor and pulled...

Ch. 8 - A typical mattress has a network of springs that...Ch. 8 - Take a spring and cut it in half to make two...Ch. 8 - A wire is stretched right to its breaking point by...Ch. 8 - Steel nails are rigid and unbending. Steel wool is...Ch. 8 - The rod in Figure Q8.15 pivots around an axle at...Ch. 8 - Two children hold opposite ends of a lightweight,...Ch. 8 - Prob. 17MCQ Ch. 8 - Prob. 18MCQ Ch. 8 - Prob. 19MCQ Ch. 8 - Prob. 20MCQ Ch. 8 - Prob. 21MCQ Ch. 8 - Prob. 22MCQ Ch. 8 - You have a heavy piece of equipment hanging from a...Ch. 8 - Prob. 24MCQ Ch. 8 - Prob. 1P Ch. 8 - Prob. 2P Ch. 8 - Prob. 3P Ch. 8 - Prob. 4P Ch. 8 - Youre carrying a 3.6-m-long, 25 kg pole to a...Ch. 8 - Prob. 6P Ch. 8 - How much torque must the pin exert to keep the rod...Ch. 8 - Prob. 8P Ch. 8 - Prob. 9P Ch. 8 - Consider the procedure for measuring a womans...Ch. 8 - Prob. 11P Ch. 8 - Prob. 12P Ch. 8 - Prob. 13P Ch. 8 - Prob. 14P Ch. 8 - Prob. 15P Ch. 8 - Prob. 16P Ch. 8 - Prob. 17P Ch. 8 - The stability of a vehicle is often rated by the...Ch. 8 - You want to slowly push a stiff board across a 20...Ch. 8 - Prob. 20P Ch. 8 - A car manufacturer claims that you can drive its...Ch. 8 - Prob. 22P Ch. 8 - One end of a spring is attached to a wall. A 25 N...Ch. 8 - An orthodontic spring, connected between the upper...Ch. 8 - Experiments using optical tweezers measure the...Ch. 8 - A spring has an unstretched length of 10 cm. It...Ch. 8 - One end of a 10-cm-long spring is attached to the...Ch. 8 - A spring stretches 5.0 cm when a 0.20 kg block is...Ch. 8 - A 1.2 kg block is hung from a vertical spring,...Ch. 8 - You need to make a spring scale to measure the...Ch. 8 - A force stretches a wire by 1.0 mm. a. A second...Ch. 8 - What hanging mass will stretch a 2.0-m-long,...Ch. 8 - How much force does it take to stretch a...Ch. 8 - An 80-cm-long, 1.0-mm-diameter steel guitar string...Ch. 8 - A student is testing a 1.0 m length of...Ch. 8 - A 1.2-m-long steel rod with a diameter of 0.50 cm...Ch. 8 - A mineshaft has an ore elevator hung from a single...Ch. 8 - The normal force of the ground on the foot can...Ch. 8 - A three-legged wooden bar stool made out of solid...Ch. 8 - Prob. 40P Ch. 8 - A glass optical fiber in a communications system...Ch. 8 - The Achilles tendon connects the muscles in your...Ch. 8 - Prob. 43GP Ch. 8 - Prob. 44GP Ch. 8 - Using the information in Figure 8.2, calculate the...Ch. 8 - A woman weighing 580 N does a pushup from her...Ch. 8 - Prob. 47GP Ch. 8 - Prob. 48GP Ch. 8 - Prob. 49GP Ch. 8 - The wheel of mass m in Figure P8.50 is pulled on...Ch. 8 - A 5.0 kg mass hanging from a spring scale is...Ch. 8 - Two identical, side-by-side springs with spring...Ch. 8 - Two springs have the same equilibrium length but...Ch. 8 - Figure P8.54 shows two springs attached to a block...Ch. 8 - A 60 kg student is standing atop a spring in an...Ch. 8 - A 25 kg child bounces on a pogo stick. The pogo...Ch. 8 - Figure P8.57 shows a lightweight plank supported...Ch. 8 - In the hammer throw, an athlete spins a heavy mass...Ch. 8 - There is a disk of cartilage between each pair of...Ch. 8 - In Example 8.1, the tension in the biceps tendon...Ch. 8 - Larger animals have sturdier bones than smaller...Ch. 8 - Orb spiders make silk with a typical diameter of...Ch. 8 - Prob. 63MSPP Ch. 8 - Prob. 64MSPP Ch. 8 - Prob. 65MSPP

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Chapter 8 Solutions