Assume a person bends forward to lift a load “with his back” as shown in Figure P12.34a. The spine pivots mainly at the fifth lumbar vertebra, with the principal supporting force provided by the erector spinalis muscle in the back. To see the magnitude of the forces involved, consider the model shown in Figure P12.34b for a person bending forward to lift a 200-N object. The spine and upper body are represented as a uniform horizontal rod of weight 350 N, pivoted at the base of the spine. The erector spinalis muscle, attached at a point two-thirds of the way up the spine, maintains the position of the back. The angle between the spine and this muscle is θ = 12.0°. Find (a) the tension T in the back muscle and (b) the compressional force in the spine. (c) Is this method a good way to lift a load? Explain your answer, using the results of parts (a) and (b). (d) Can you suggest a better method to lift a load? Figure P12.34

BuyFind

Physics for Scientists and Enginee...

10th Edition
Raymond A. Serway + 1 other
Publisher: Cengage Learning
ISBN: 9781337553292
BuyFind

Physics for Scientists and Enginee...

10th Edition
Raymond A. Serway + 1 other
Publisher: Cengage Learning
ISBN: 9781337553292

Solutions

Chapter
Section
Chapter 12, Problem 34AP
Textbook Problem

Assume a person bends forward to lift a load “with his back” as shown in Figure P12.34a. The spine pivots mainly at the fifth lumbar vertebra, with the principal supporting force provided by the erector spinalis muscle in the back. To see the magnitude of the forces involved, consider the model shown in Figure P12.34b for a person bending forward to lift a 200-N object. The spine and upper body are represented as a uniform horizontal rod of weight 350 N, pivoted at the base of the spine. The erector spinalis muscle, attached at a point two-thirds of the way up the spine, maintains the position of the back. The angle between the spine and this muscle is θ = 12.0°. Find (a) the tension T in the back muscle and (b) the compressional force in the spine. (c) Is this method a good way to lift a load? Explain your answer, using the results of parts (a) and (b). (d) Can you suggest a better method to lift a load?

Figure P12.34

Chapter 12, Problem 34AP, Assume a person bends forward to lift a load with his back as shown in Figure P12.34a. The spine

Expert Solution

Want to see the full answer?

Check out a sample textbook solution.

Want to see this answer and more?

Experts are waiting 24/7 to provide step-by-step solutions in as fast as 30 minutes!*

*Response times vary by subject and question complexity. Median response time is 34 minutes and may be longer for new subjects.

Chapter 12 Solutions

Physics for Scientists and Engineers with Modern Physics
Ch. 12 - Find the mass m of the counterweight needed to...Ch. 12 - A uniform beam of length L and mass m shown in...Ch. 12 - A flexible chain weighing 40.0 N hangs between two...Ch. 12 - A 20.0-kg floodlight in a park is supported at the...Ch. 12 - Sir Lost-a-Lot dons his armor and sets out from...Ch. 12 - Review. While Lost-a-Lot ponders his next move in...Ch. 12 - Figure P12.13 shows a claw hammer being used to...Ch. 12 - A 10.0-kg monkey climbs a uniform ladder with...Ch. 12 - John is pushing his daughter Rachel in a...Ch. 12 - Figure P12.15 Problems 15 and 16. John is pushing...Ch. 12 - The deepest point in the ocean is in the Mariana...Ch. 12 - A steel wire of diameter 1 mm can support a...Ch. 12 - A child slides across a floor in a pair of...Ch. 12 - Evaluate Youngs modulus for the material whose...Ch. 12 - Assume if the shear stress in steel exceeds about...Ch. 12 - When water freezes, it expands by about 9.00%....Ch. 12 - Review. A 30.0-kg hammer, moving with speed 20.0...Ch. 12 - A uniform beam resting on two pivots has a length...Ch. 12 - A bridge of length 50.0 m and mass 8.00 104 kg is...Ch. 12 - In exercise physiology studies, it is sometimes...Ch. 12 - The lintel of prestressed reinforced concrete in...Ch. 12 - The following equations are obtained from a force...Ch. 12 - A hungry bear weighing 700 N walks out on a beam...Ch. 12 - A 1 200-N uniform boom at = 65 to the vertical is...Ch. 12 - A uniform sign of weight Fg and width 2L hangs...Ch. 12 - When a person stands on tiptoe on one foot (a...Ch. 12 - A 10 000-N shark is supported by a rope attached...Ch. 12 - Assume a person bends forward to lift a load with...Ch. 12 - A uniform beam of mass m is inclined at an angle ...Ch. 12 - Why is the following situation impossible? A...Ch. 12 - When a circus performer performing on the rings...Ch. 12 - Figure P12.38 shows a light truss formed from...Ch. 12 - One side of a plant shelf is supported by a...Ch. 12 - A stepladder of negligible weight is constructed...Ch. 12 - A stepladder of negligible weight is constructed...Ch. 12 - Review. A wire of length L, Youngs modulus Y, and...Ch. 12 - Two racquetballs, each having a mass of 170 g, are...Ch. 12 - Consider the rectangular cabinet of Problem 36...Ch. 12 - Review. An aluminum wire is 0.850 m long and has a...Ch. 12 - You have been hired as an expert witness in a case...Ch. 12 - A 500-N uniform rectangular sign 4.00 m wide and...Ch. 12 - A steel cable 3.00 cm2 in cross-sectional area has...Ch. 12 - A uniform rod of weight Fg and length L is...Ch. 12 - In the What If? section of Example 12.2, let d...

Additional Science Textbook Solutions

Find more solutions based on key concepts
Some meteorites contain organic molecules. What does that mean?

Foundations of Astronomy (MindTap Course List)

The pressure gauge on a cylinder of gas registers the gauge pressure, which is the difference between the inter...

Physics for Scientists and Engineers, Technology Update (No access codes included)

What would a standing wave look like in a rectangular swimming pool?

Oceanography: An Invitation To Marine Science, Loose-leaf Versin

Tracheids are part of ______. a. cortex b. mesophyll c. phloem d. xylem

Biology: The Unity and Diversity of Life (MindTap Course List)

Describe a situation when the intake of a phytochemical supplement or a functional food would be appropriate. G...

Nutrition: Concepts and Controversies - Standalone book (MindTap Course List)

What are some functions of skin?

Human Biology (MindTap Course List)

How does binge-eating disorder differ from bulimia nervosa?

Nutrition Through the Life Cycle (MindTap Course List)