Physics: Principles with Applications
7th Edition
ISBN: 9780321625922
Author: Douglas C. Giancoli
Publisher: Addison-Wesley
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Chapter 9, Problem 13Q
Why is it more difficult to do sit-ups when your knees are bent than when your legs are stretched out?
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Chapter 9 Solutions
Physics: Principles with Applications
Ch. 9 - Prob. 1OQCh. 9 - Describe several situations in which an object is...Ch. 9 - Prob. 2QCh. 9 - You can find the center of gravity of a meter...Ch. 9 - Prob. 4QCh. 9 - A ground retaining wall is shown in Fig. 9-36a...Ch. 9 - Can the sum of the torques on an object be zero...Ch. 9 - A ladder, leaning against a wall, makes a 60°...Ch. 9 - A uniform meter stick supported at the 25-cm mark...Ch. 9 - Why do you tend to lean backward when carrying a...
Ch. 9 - Figure 9-38 shows a cone. Explain how to lay it on...Ch. 9 - Prob. 11QCh. 9 - Why is it not possible to sit upright in a chair...Ch. 9 - Why is it more difficult to do sit-ups when your...Ch. 9 - Explain why touching your toes while you are...Ch. 9 - Prob. 15QCh. 9 - Name the type of equilibrium for each position of...Ch. 9 - (
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Is the Young's modulus for a bungee cord...Ch. 9 - Prob. 18QCh. 9 - Prob. 19QCh. 9 - A 60-kg woman stands on the very end of a uniform...Ch. 9 - Prob. 2MCQCh. 9 - Prob. 3MCQCh. 9 - Prob. 4MCQCh. 9 - Two children are balanced on opposite sides of a...Ch. 9 - Prob. 6MCQCh. 9 - Prob. 7MCQCh. 9 - Prob. 8MCQCh. 9 - Prob. 9MCQCh. 9 - Prob. 10MCQCh. 9 - Three forces are applied to a tree sapling, as...Ch. 9 - Prob. 2PCh. 9 - 3(I) A tower crane ( Fig. 9-48a) must always be...Ch. 9 - What is the mass of the diver in Fig. 9-49 if she...Ch. 9 - Prob. 5PCh. 9 - Figure 9-50 shows a pair of forceps used to hold a...Ch. 9 - Prob. 7PCh. 9 - The two trees in Fig. 9-51 are 6.6 m apart. A...Ch. 9 - Prob. 9PCh. 9 - Prob. 10PCh. 9 - Prob. 11PCh. 9 - Find the tension in the two cords shown in Fig....Ch. 9 - Prob. 13PCh. 9 - Prob. 14PCh. 9 - The force required to pull the cork out of the top...Ch. 9 - Prob. 16PCh. 9 - Three children are trying to balance on a seesaw,...Ch. 9 - A shop sign weighing 215 N hangs from the end of a...Ch. 9 - Prob. 19PCh. 9 - Prob. 20PCh. 9 - Prob. 21PCh. 9 - 22 (II) A 20.0-m-long uniform beam weighing 650 N...Ch. 9 - Prob. 23PCh. 9 - Prob. 24PCh. 9 - Prob. 25PCh. 9 - Prob. 26PCh. 9 - A uniform rod AB of length 5.0 m and mass M=3.S kg...Ch. 9 - You are on a pirate ship and being forced to walk...Ch. 9 - Prob. 29PCh. 9 - Prob. 30PCh. 9 - Prob. 31PCh. 9 - Prob. 32PCh. 9 - Prob. 33PCh. 9 - Prob. 34PCh. 9 - Prob. 35PCh. 9 - 36 (II) The Achilles tendon is attached to the...Ch. 9 - If 25 kg is the maximum mass m that a person can...Ch. 9 - Prob. 38PCh. 9 - Prob. 39PCh. 9 - Prob. 40PCh. 9 - A marble column of cross-sectional area 1.4 m2...Ch. 9 - Prob. 42PCh. 9 - A sign (mass 1700 kg) hangs from the bottom end of...Ch. 9 - Prob. 44PCh. 9 - Prob. 45PCh. 9 - Prob. 46PCh. 9 - A steel wire 2.3 mm in diameter stretches by...Ch. 9 - Prob. 48PCh. 9 - Prob. 49PCh. 9 - Prob. 50PCh. 9 - Prob. 51PCh. 9 - Prob. 52PCh. 9 - (a) What is the minimum cross-sectional area...Ch. 9 - Prob. 54PCh. 9 - Prob. 55PCh. 9 - Prob. 56PCh. 9 - Prob. 57PCh. 9 - Prob. 58GPCh. 9 - Prob. 59GPCh. 9 - Prob. 60GPCh. 9 - Prob. 61GPCh. 9 - Prob. 62GPCh. 9 - Prob. 63GPCh. 9 - Prob. 64GPCh. 9 - When a mass of 25 kg is hung from the middle of a...Ch. 9 - Prob. 66GPCh. 9 - Prob. 67GPCh. 9 - Prob. 68GPCh. 9 - Prob. 69GPCh. 9 - Prob. 70GPCh. 9 - Prob. 71GPCh. 9 - Prob. 72GPCh. 9 - Prob. 73GPCh. 9 - A 2.0-m-high box with a 1.0-m-square base is moved...Ch. 9 - Prob. 75GPCh. 9 - Prob. 76GPCh. 9 - Prob. 77GPCh. 9 - Prob. 78GPCh. 9 - In a mountain-climbing technique called the...Ch. 9 - Prob. 80GPCh. 9 - A cubic crate of side s=20m is top-heavy: its cgis...
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- When you carry a heavy load with one arm, why do you tend to hold your free arm away from your body?arrow_forwardA 75-kg man stands on his toes by exerting an upward force through the Achilles tendon, as shown. What is the force in the Achilles tendon if he stands on one foot?arrow_forwardWhen throwing a football you are always instructed to follow-through. What is the advantage of this? You are also instructed to stand with your feet about shoulder-width apart. What is the advantage of this?arrow_forward
- Why must you bend forward while carrying a heavy load on your back?arrow_forwardWhy Does A Cyclist Lean To One Side, While Going Along A Curve? In What Direction Does He Lean?arrow_forwardAssuming your feet are not held down, which is more difficult: doing sit-ups with your knees bent or with your legs straight out?arrow_forward
- A woman wearing a stiletto heel shoes (heel pointed shoes) gets tired and will feel pain in her legs easily. Why so?arrow_forwardDuring a circus act, one performer swings upside down hanging from a trapeze while holding another performer, also upside-down, by the calves. The legs (femurs) of the lower performer undergo deformation due to the upward force from the upper performer. If the upward force on the lower performer's legs is 3mg (three times her weight), how much do the bones (the femurs) in her upper legs stretch in meters? You may assume each bone is equivalent to a uniform rod 34 cm long and 1.75 cm in radius and the legs are massless, serving only to transmit the upward force on the torso. Her mass is 62 kg and Young's modulus for tension on bones is 1.6 × 1010 N/m2. ΔL =arrow_forwardThere is a small but appreciable amount of elastic hysteresis in the large tendon at the back of a horse’s leg. Explain how this can cause damage to the tendon if a horse runs too hard for too long a time.arrow_forward
- 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_forwardWhy is it important to secure file cabinets to the floor, especially cabinets with heavy loads in top drawers?arrow_forwardA fireman at the scene of a fire is holding a heavy hose out of which water is gushing. To keep hisbalance, he often has to lean. Which way does he lean, forward or backward, and why?arrow_forward
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