College Physics
2nd Edition
ISBN: 9780134601823
Author: ETKINA, Eugenia, Planinšič, G. (gorazd), Van Heuvelen, Alan
Publisher: Pearson,
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Textbook Question
Chapter 8, Problem 20CQ
Is it more difficult to do a sit-up with your hands stretched in front of you or with them behind your head? Explain.
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Chapter 8 Solutions
College Physics
Ch. 8 - Prob. 1RQCh. 8 - Review Question 8.2 Give an example of a situation...Ch. 8 - Review Question 8.3 You read the following...Ch. 8 - Prob. 4RQCh. 8 - Review Question 8.5 You are trying to hold a heavy...Ch. 8 - Review Question 8.6 Why is a ball hanging by a...Ch. 8 - A falling leaf usually flutters while falling....Ch. 8 - Prob. 2MCQCh. 8 - A hammock is tied with ropes between two trees. A...Ch. 8 - Prob. 4MCQ
Ch. 8 - 5. A physics textbook lies on top of a chemistry...Ch. 8 - What does it mean if the torque of a force is...Ch. 8 - Prob. 7MCQCh. 8 - 8. Why do you tilt your body forward when hiking...Ch. 8 - 9. What does it mean if the torque of a 10-N force...Ch. 8 - What is the maximum angle to the horizontal you...Ch. 8 - Prob. 11MCQCh. 8 - 12. Is it possible for an object not to be in...Ch. 8 - Explain the meaning of torque so that a friend not...Ch. 8 - Prob. 14CQCh. 8 - What are the two conditions of equilibrium? What...Ch. 8 - Give three examples of situations in which an...Ch. 8 - The force that the body muscles exert on bones...Ch. 8 - A ladder leans against a wall. Construct a force...Ch. 8 - Using a crowbar, a person can remove a nail by...Ch. 8 - 20. Is it more difficult to do a sit-up with your...Ch. 8 - Sit on a chair with your feet straight down at the...Ch. 8 - Can you balance the tip of a wooden ruler...Ch. 8 - Try to balance a sharp wooden pencil on your...Ch. 8 - 24. Design a device that you can use to...Ch. 8 - Explain why it is easier to keep your balance...Ch. 8 - A carpenters trick to keep nails from bending when...Ch. 8 - Determine the torques about the axis of rotation P...Ch. 8 - 2. Three 200-N forces are exerted on the beam...Ch. 8 - 3. * A 2.0-m-long, 15-kg ladder is resting against...Ch. 8 - Figure P8.4 shows two different situations where...Ch. 8 - Three friends tie three ropes in a knot and pull...Ch. 8 - Prob. 6PCh. 8 - * Kate joins Jim, Luis, and Adrienne in the...Ch. 8 - You hang a light in front of your house using an...Ch. 8 - * Find the values of the forces the ropes exert on...Ch. 8 - Prob. 10PCh. 8 - Determine the masses m1 and m2 of the two objects...Ch. 8 - * Lifting an engine You work in a machine shop and...Ch. 8 - 13. * More lifting You exert a 630-N force on rope...Ch. 8 - Prob. 14PCh. 8 - 15. * Tightrope walking A tightrope walker wonders...Ch. 8 - 16. * Lifting patients An apparatus to lift...Ch. 8 - 17. A father (80 kg), mother (56 kg), daughter (16...Ch. 8 - Prob. 18PCh. 8 - * You place a 3.0-m-long board symmetrically...Ch. 8 - Prob. 20PCh. 8 - Prob. 21PCh. 8 - Prob. 22PCh. 8 - 23. EST Compare the two different designs of...Ch. 8 - Ray decides to paint the outside of his uncles...Ch. 8 - 25. * A 2.0-m-long uniform beam of mass 8.0 kg...Ch. 8 - * A uniform beam of length / and mass m supports a...Ch. 8 - Prob. 27PCh. 8 - Prob. 28PCh. 8 - Prob. 29PCh. 8 - Prob. 30PCh. 8 - 31. * An 80-kg clown sits on a 20-kg bike on a...Ch. 8 - s center of mass? (Hint: You can think of cutting...Ch. 8 - Leg support A persons broken leg is kept in place...Ch. 8 - Prob. 34PCh. 8 - Prob. 35PCh. 8 - * If the force F shown in Figure P8.35 is 840 N...Ch. 8 - Prob. 37PCh. 8 - 38. * You decide to hang another plant from a...Ch. 8 - Prob. 39PCh. 8 - * What mechanical work must you do to lift a log...Ch. 8 - 41. * A 70-g meter stick has a 30-g piece of...Ch. 8 - * You are trying to tilt a very tall refrigerator...Ch. 8 - Prob. 43PCh. 8 - 44. * You have an Atwood machine (see Figure 4.9 )...Ch. 8 - * EST You stand sideways in a moving train....Ch. 8 - 46. EST Your hand holds a liter of milk (mass...Ch. 8 - EST Body torque You hold a 4.0-kg computer....Ch. 8 - Prob. 48GPCh. 8 - 49. BIO Using triceps to push a table A man pushes...Ch. 8 - Prob. 50GPCh. 8 - Prob. 51GPCh. 8 - Prob. 52GPCh. 8 - 53.* BIO Dumbbell lift IA woman lifts a 3.6-kg...Ch. 8 - s shoulder joint exerts on her humerus.Ch. 8 - Prob. 55GPCh. 8 - * Eiichi has purchased an adjustable hand grip to...Ch. 8 - 57. *BIO While browsing books on neurophysiology,...Ch. 8 - 58. ** Touch detector You have two force sensors...Ch. 8 - * An 80-kg person stands at one end of a 130-kg...Ch. 8 - 61. EST Two people (50 kg and 75 kg) holding hands...Ch. 8 - Prob. 62GPCh. 8 - BIO Muscles work in pairs Skeletal muscles produce...Ch. 8 - BIO Muscles work in pairs Skeletal muscles produce...Ch. 8 - BIO Muscles work in pairs Skeletal muscles produce...Ch. 8 - BIO Muscles work in pairs Skeletal muscles produce...Ch. 8 - BIO Improper lifting and the back A careful study...Ch. 8 - BIO Improper lifting and the back A careful study...Ch. 8 - BIO Improper lifting and the back A careful study...Ch. 8 - BIO Improper lifting and the back A careful study...
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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_forwardBIO When a gymnast performing on the rings executes the iron cross, he maintains the position at rest shown in Figure P10.85a. In this maneuver, the gymnasts feet (not shown) are off the floor. The primary muscles involved in supporting this position are the latissimus dorsi (lats) and the pectoralis major (pecs). One of the rings exerts an upward fore Fh on a hand as shown in Figure P10.85b. The force Fs is exerted by the shoulder joint on the arm. The latissimus dorsi and pectoralis major muscles exert a total force Fm on the arm. (a) Using the information in the figure, find the magnitude of the force Fm. (b) Suppose an athlete in training cannot perform the iron cross but can hold a position similar to the figure in which the arms make a 45 angle with the horizontal rather than being horizontal. Why is this position easier for the athlete? Figure P10.85arrow_forwardQ.2) Answer the following questions: a) Why does any person lean towards right while carrying a bag in her left hand?arrow_forward
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- 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 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_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 = 210–N object. The spine and upper body are represented as a uniform horizontal rod of weight Wb = 325 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 12.0arrow_forward
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