Physics for Scientists and Engineers, Technology Update (No access codes included)
9th Edition
ISBN: 9781305116399
Author: Raymond A. Serway, John W. Jewett
Publisher: Cengage Learning
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Chapter 12, Problem 12.4CQ
To determine
The reason a person can’t bend forward without falling by putting their heels firmly against the wall.
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A ladder, leaning against a wall, makes a 60° angle with theground. When is it more likely to slip: when a person standson the ladder near the top or near the bottom? Explain.
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spine, maintains the position of the back. The angle between the spine and this muscle is 12.0°
Back muscle
Pivot
R₂
T120
T
W
W₂
0
(a) Find the tension in the back muscle.
KN
D
(b) Find the compressional force in the spine. (Enter the magnitude.)
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Chapter 12 Solutions
Physics for Scientists and Engineers, Technology Update (No access codes included)
Ch. 12 - Consider the object subject to the two forces of...Ch. 12 - Consider the object subject to the three forces in...Ch. 12 - A meterstick of uniform density is hung from a...Ch. 12 - For the three parts of this Quick Quiz, choose...Ch. 12 - The acceleration due to gravity becomes weaker by...Ch. 12 - A rod 7.0 in long is pivoted at a point 2.0 m from...Ch. 12 - Prob. 12.3OQCh. 12 - Two forces are acting on an object. Which of the...Ch. 12 - Prob. 12.5OQCh. 12 - A 20.0-kg horizontal plank 4.00 in long rests on...
Ch. 12 - Prob. 12.7OQCh. 12 - In analyzing the equilibrium of a flat, rigid...Ch. 12 - A certain wire, 3 m long, stretches by 1.2 mm when...Ch. 12 - The center of gravity of an ax is on the...Ch. 12 - A ladder stands on the ground, leaning against a...Ch. 12 - Prob. 12.2CQCh. 12 - (a) Give an example in which the net force acting...Ch. 12 - Prob. 12.4CQCh. 12 - Prob. 12.5CQCh. 12 - A girl has a large, docile dog she wishes to weigh...Ch. 12 - Prob. 12.7CQCh. 12 - What kind of deformation does a cube of Jell-O...Ch. 12 - What are the necessary conditions for equilibrium...Ch. 12 - Why is the following situation impossible? A...Ch. 12 - Prob. 12.3PCh. 12 - Prob. 12.4PCh. 12 - Your brother is opening a skateboard shop. He has...Ch. 12 - A circular pizza of radius R has a circular piece...Ch. 12 - Prob. 12.7PCh. 12 - Prob. 12.8PCh. 12 - Prob. 12.9PCh. 12 - Prob. 12.10PCh. 12 - A uniform beam of length 7.60 m and weight 4.50 ...Ch. 12 - A vaulter holds a 29.4-N pole in equilibrium by...Ch. 12 - A 15.0-in uniform ladder weighing 500 N rests...Ch. 12 - A uniform ladder of length L.and mass m1 rests...Ch. 12 - A flexible chain weighing 40.0 N hangs between two...Ch. 12 - A uniform beam of length L and mass m shown in...Ch. 12 - Figure P12.13 shows a claw hammer being used to...Ch. 12 - A 20.0-kg floodlight in a park is supported at the...Ch. 12 - Prob. 12.19PCh. 12 - Review. While Lost-a-Lot ponders his next move in...Ch. 12 - John is pushing his daughter Rachel in a...Ch. 12 - Prob. 12.22PCh. 12 - One end of a uniform 4.00-m-long rod of weight Fg...Ch. 12 - A 10.0-kg monkey climbs a uniform ladder with...Ch. 12 - A uniform plank of length 2.00 m and mass 30.0 kg...Ch. 12 - A steel wire of diameter 1 mm can support a...Ch. 12 - The deepest point in the ocean is in the Mariana...Ch. 12 - Assume Youngs modulus for bone is 1.50 1010 N/m2....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 - A 200-kg load is hung on a wire of length 4.00m,...Ch. 12 - A walkway suspended across a hotel lobby is...Ch. 12 - Review. A 2.00-m-long cylindrical steel wire with...Ch. 12 - Review. A 30.0-kg hammer, moving with speed 20.0...Ch. 12 - A bridge of length 50.0 m and mass 8.00 104 kg is...Ch. 12 - A uniform beam resting on two pivots has a length...Ch. 12 - Prob. 12.39APCh. 12 - The lintel of prestressed reinforced concrete in...Ch. 12 - Prob. 12.41APCh. 12 - When a person stands on tiptoe on one foot (a...Ch. 12 - A hungry bear weighing 700 N walks out on a beam...Ch. 12 - The following equations are obtained from a force...Ch. 12 - A uniform sign of weight Fg and width 2L hangs...Ch. 12 - A 1 200-N uniform boom at = 65 to the vertical is...Ch. 12 - Prob. 12.47APCh. 12 - Assume a person bends forward to lift a load with...Ch. 12 - A 10 000-N shark is supported by a rope attached...Ch. 12 - Why is the following situation impossible? A...Ch. 12 - A uniform beam of mass m is inclined at an angle ...Ch. 12 - Prob. 12.52APCh. 12 - When a circus performer performing on the rings...Ch. 12 - Figure P12.38 shows a light truss formed from...Ch. 12 - Prob. 12.55APCh. 12 - A stepladder of negligible weight is constructed...Ch. 12 - A stepladder of negligible weight is constructed...Ch. 12 - (a) Estimate the force with which a karate master...Ch. 12 - Two racquetballs, each having a mass of 170 g, are...Ch. 12 - Review. A wire of length L, Youngs modulus Y, and...Ch. 12 - Review. An aluminum wire is 0.850 m long and has a...Ch. 12 - Prob. 12.62APCh. 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 pole is propped between the floor and...Ch. 12 - In the What If? section of Example 12.2, let d...Ch. 12 - Figure P12.67 shows a vertical force applied...Ch. 12 - A uniform rod of weight Fg and length L is...
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- The bones of the forearm (radius and ulna) are hinged to the humerus at the elbow. The biceps muscle connects to the bones of the forearm about 2.15 cm beyond the joint. Assume the forearm has a mass of 2.35 kg and a length of 0.445 m.When the humerus and the biceps are nearly vertical and the forearm is horizontal, if a person wishes to hold an object of mass 4.95 kg so that her forearm remains motionless, what is the force exerted by the biceps muscle?arrow_forwardAs a part of his daily workout routine, he lifts 10-kg dumbbells on each hand. His hands and forearms weigh 4 kg each. If the length of each of his forearms and hands are 0.5 m, determine the force exerted by his muscles? Assume that the center of gravity of the forrearms are in the middle.arrow_forwardA person bending forward to lift a load "with his back" (Figure a) rather than "with his knees" can be injured by large forces exerted on the muscles and vertebrae. 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, and to understand why back problems are common among humans, consider the model shown in Figure b, of a person bending forward to lift a Wo = 215–N object. The spine and upper body are represented as a uniform horizontal rod of weight Wb = 330 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 12.0°. (a) Find the tension in the back muscle. (b) Find the compressional force in the spine. (Enter the magnitude.)arrow_forward
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