Physics for Scientists and Engineers With Modern Physics
9th Edition
ISBN: 9781133953982
Author: SERWAY, Raymond A./
Publisher: Cengage Learning
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Chapter 12, Problem 4CQ
To determine
The condition when you put your heels firmly against the wall and then bend forward.
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Why can’t you put your heels firmly against a wall and then bend over without falling?
You can find the center of gravity of a meter stick by resting it horizontally on your two index fingers, and then slowly drawing your fingers together. First the meter stick will slip on one finger, and then on the other, but eventually the fingers meet at the CG. Why does this work?
Stand with your heels and back against a wall and try to bend over and touch your toes. You’ll find that you have to stand away from the wall to do so without toppling over. Compare the minimum distance of your heels from the wall with the distance for a friend of the opposite sex. Who can touch their toes with their heels nearer to the wall: men or women? On the average and in proportion to height, which sex has the lower center of gravity?
Chapter 12 Solutions
Physics for Scientists and Engineers With Modern Physics
Ch. 12.1 - Consider the object subject to the two forces of...Ch. 12.1 - Consider the object subject to the three forces in...Ch. 12.2 - A meterstick of uniform density is hung from a...Ch. 12.4 - For the three parts of this Quick Quiz, choose...Ch. 12 - Prob. 1OQCh. 12 - Prob. 2OQCh. 12 - Prob. 3OQCh. 12 - Prob. 4OQCh. 12 - In the cabin of a ship, a soda can rests in a...Ch. 12 - Prob. 6OQ
Ch. 12 - Prob. 7OQCh. 12 - Prob. 8OQCh. 12 - Prob. 9OQCh. 12 - Prob. 10OQCh. 12 - Prob. 1CQCh. 12 - Prob. 2CQCh. 12 - Prob. 3CQCh. 12 - Prob. 4CQCh. 12 - Prob. 5CQCh. 12 - Prob. 6CQCh. 12 - Prob. 7CQCh. 12 - What kind of deformation does a cube of Jell-O...Ch. 12 - Prob. 1PCh. 12 - Why is the following situation impossible? A...Ch. 12 - Prob. 3PCh. 12 - Prob. 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. 7PCh. 12 - Prob. 8PCh. 12 - Prob. 9PCh. 12 - Prob. 10PCh. 12 - A uniform beam of length 7.60 m and weight 4.50 ...Ch. 12 - Prob. 12PCh. 12 - Prob. 13PCh. 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. 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. 22PCh. 12 - Prob. 23PCh. 12 - A 10.0-kg monkey climbs a uniform ladder with...Ch. 12 - Prob. 25PCh. 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 - Prob. 31PCh. 12 - When water freezes, it expands by about 9.00%....Ch. 12 - Prob. 33PCh. 12 - Prob. 34PCh. 12 - Prob. 35PCh. 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. 39APCh. 12 - The lintel of prestressed reinforced concrete in...Ch. 12 - Prob. 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 - Prob. 44APCh. 12 - A uniform sign of weight Fg and width 2L hangs...Ch. 12 - Prob. 46APCh. 12 - Prob. 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 - Prob. 50APCh. 12 - A uniform beam of mass m is inclined at an angle ...Ch. 12 - Prob. 52APCh. 12 - When a circus performer performing on the rings...Ch. 12 - Figure P12.38 shows a light truss formed from...Ch. 12 - Prob. 55APCh. 12 - A stepladder of negligible weight is constructed...Ch. 12 - A stepladder of negligible weight is constructed...Ch. 12 - Prob. 58APCh. 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. 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 - Prob. 65CPCh. 12 - In the What If? section of Example 12.2, let d...Ch. 12 - Prob. 67CPCh. 12 - A uniform rod of weight Fg and length L is...
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- Stand with your heels and back against a wall and try to bend over and touch your toes. You’ll find that you have to stand away from the wall to do so without toppling over. Compare the minimum distance of your heels from the wall with that of a friend of the opposite sex. Who can touch their toes with their heels nearer to the wall males or females? On the average and in proportion to height, which sex has the lower center of gravity?arrow_forwardA 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.arrow_forwardThe 3 m long uniform plank is supported by a fulcrum at the midpoint. Where should a 45 kg student must be from the midpoint to be able to balance the plank? 45 kg X = ? +0.4 m +0.5 m 30 kg 40 kgarrow_forward
- Activity: Stand straight with your heels, back, and head against a wall. Bend forward from your waist, keeping your heels and Bottom against the wall, to touch your toes. Can you do this without toppling over? Explain why and what you need to do to be able to touch your toes without losing your balance. Is it easier for a woman to do this?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 W-195-N object. The spine and upper body are represented as a uniform horizontal rod of weight W-295 N pivoted at the base of the spine. The erector spinalls 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° 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.) KNarrow_forwardWhen you turn while running, you must lean in the direction of the turn or risk falling over. If you lean left as you turn left, why don’t you fall over to the left?arrow_forward
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- A person places a bathroom scale in the center of the floor and stands on the scale with his arms at his sides. If he keeps his arms rigid and quickly moves them up and over his head, he notices the scale reading increase as he brings his arms upward? Why? Then , with his arms over his head, he quickly lowers his arms to his side, How does the scale reading change and why?arrow_forwardYou can find the center of gravity of a long ruler by resting it horizontally on your two index fingers, and then slowly drawing your fingers together. First the ruler will slip on one finger, and then on the other, but eventually the fingers meet at the CG. Why does this workarrow_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 = 195-N object. The spine and upper body are represented as a uniform horizontal rod of weight W₁ = 305 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 12.0⁰. Back muscle R₂ T 12.0° 1T Rx Pivot a Wb Wo ..(a).Find the tension in the back muscle. 1.114 Enter a number. differs from the correct answer by more than 10%. Double check your calculations. kN…arrow_forward
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