Student Workbook for College Physics: A Strategic Approach Volume 1 (Chs. 1-16)
3rd Edition
ISBN: 9780321908865
Author: Randall D. Knight (Professor Emeritus), Brian Jones, Stuart Field
Publisher: PEARSON
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Chapter 8, Problem 5CQ
To determine
To explain: The cause for the extension of arms by the divers in front of them.
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A refrigerator of width w and height h rests on a rough incline as in Figure P8.25. Find an expression for the maximum value 0 can have before the refrigerator tips over. Note, the contact point between the refrigerator and incline shifts as 0 increases and treat the refrigerator as a uniform box.
When you carry shopping bags, rather than grasp the handles with your hand as in Q8.14a, you might choose to put them over your arm and slide the handle toward your elbow as in Q8.14b. Explain why this leads to less muscle effort to carry the bags and less force in your elbow joint.
The main muscles that hold your head upright attach to your spine in back of the point where your head pivots on your neck. Figure P8.66 shows typical numbers for the distance from the pivot to the muscle attachment point and the distance from the pivot to the center of gravity of the head. The muscles pull down to keep your head upright. If the muscle relaxes—if, for instance, you doze in one of your classes besides Physics—your head tips forward. In the questions that follow, assume that your head has a mass of 4.8 kg, and that you maintain the relative angle between your head and your spine.
a. With the head held level, as shown, what muscle force is needed to keep a 4.8 kg head upright?b. If you tip your body forward so that your spine is level with the ground, what muscle force is needed to keep your head in the same orientation relative to the spine?c. If you tip your body backward, you will reach a point where no muscle force is needed to keep your head upright. For the…
Chapter 8 Solutions
Student Workbook for College Physics: A Strategic Approach Volume 1 (Chs. 1-16)
Ch. 8 - An object is acted upon by two (and only two)...Ch. 8 - Prob. 2CQCh. 8 - Could a ladder on a level floor lean against a...Ch. 8 - If you are using a rope to raise a tall mast,...Ch. 8 - Prob. 5CQCh. 8 - Prob. 6CQCh. 8 - Prob. 7CQCh. 8 - A spring exerts a 10 N force after being stretched...Ch. 8 - The left end of a spring is attached to a wall....Ch. 8 - A spring is attached to the floor and pulled...
Ch. 8 - A typical mattress has a network of springs that...Ch. 8 - Take a spring and cut it in half to make two...Ch. 8 - A wire is stretched right to its breaking point by...Ch. 8 - Steel nails are rigid and unbending. Steel wool is...Ch. 8 - The rod in Figure Q8.15 pivots around an axle at...Ch. 8 - Two children hold opposite ends of a lightweight,...Ch. 8 - Prob. 17MCQCh. 8 - Prob. 18MCQCh. 8 - Prob. 19MCQCh. 8 - Prob. 20MCQCh. 8 - Prob. 21MCQCh. 8 - Prob. 22MCQCh. 8 - You have a heavy piece of equipment hanging from a...Ch. 8 - Prob. 24MCQCh. 8 - Prob. 1PCh. 8 - Prob. 2PCh. 8 - Prob. 3PCh. 8 - Prob. 4PCh. 8 - Youre carrying a 3.6-m-long, 25 kg pole to a...Ch. 8 - Prob. 6PCh. 8 - How much torque must the pin exert to keep the rod...Ch. 8 - Prob. 8PCh. 8 - Prob. 9PCh. 8 - Consider the procedure for measuring a womans...Ch. 8 - Prob. 11PCh. 8 - Prob. 12PCh. 8 - Prob. 13PCh. 8 - Prob. 14PCh. 8 - Prob. 15PCh. 8 - Prob. 16PCh. 8 - Prob. 17PCh. 8 - The stability of a vehicle is often rated by the...Ch. 8 - You want to slowly push a stiff board across a 20...Ch. 8 - Prob. 20PCh. 8 - A car manufacturer claims that you can drive its...Ch. 8 - Prob. 22PCh. 8 - One end of a spring is attached to a wall. A 25 N...Ch. 8 - An orthodontic spring, connected between the upper...Ch. 8 - Experiments using optical tweezers measure the...Ch. 8 - A spring has an unstretched length of 10 cm. It...Ch. 8 - One end of a 10-cm-long spring is attached to the...Ch. 8 - A spring stretches 5.0 cm when a 0.20 kg block is...Ch. 8 - A 1.2 kg block is hung from a vertical spring,...Ch. 8 - You need to make a spring scale to measure the...Ch. 8 - A force stretches a wire by 1.0 mm. a. A second...Ch. 8 - What hanging mass will stretch a 2.0-m-long,...Ch. 8 - How much force does it take to stretch a...Ch. 8 - An 80-cm-long, 1.0-mm-diameter steel guitar string...Ch. 8 - A student is testing a 1.0 m length of...Ch. 8 - A 1.2-m-long steel rod with a diameter of 0.50 cm...Ch. 8 - A mineshaft has an ore elevator hung from a single...Ch. 8 - The normal force of the ground on the foot can...Ch. 8 - A three-legged wooden bar stool made out of solid...Ch. 8 - Prob. 40PCh. 8 - A glass optical fiber in a communications system...Ch. 8 - The Achilles tendon connects the muscles in your...Ch. 8 - Prob. 43GPCh. 8 - Prob. 44GPCh. 8 - Using the information in Figure 8.2, calculate the...Ch. 8 - A woman weighing 580 N does a pushup from her...Ch. 8 - Prob. 47GPCh. 8 - Prob. 48GPCh. 8 - Prob. 49GPCh. 8 - The wheel of mass m in Figure P8.50 is pulled on...Ch. 8 - A 5.0 kg mass hanging from a spring scale is...Ch. 8 - Two identical, side-by-side springs with spring...Ch. 8 - Two springs have the same equilibrium length but...Ch. 8 - Figure P8.54 shows two springs attached to a block...Ch. 8 - A 60 kg student is standing atop a spring in an...Ch. 8 - A 25 kg child bounces on a pogo stick. The pogo...Ch. 8 - Figure P8.57 shows a lightweight plank supported...Ch. 8 - In the hammer throw, an athlete spins a heavy mass...Ch. 8 - There is a disk of cartilage between each pair of...Ch. 8 - In Example 8.1, the tension in the biceps tendon...Ch. 8 - Larger animals have sturdier bones than smaller...Ch. 8 - Orb spiders make silk with a typical diameter of...Ch. 8 - Prob. 63MSPPCh. 8 - Prob. 64MSPPCh. 8 - Prob. 65MSPP
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- When a person stands on tiptoe (a strenuous position), the position of the foot is as shown in Figure P8.24a. The total gravitational force on the body, Fg, is supported by the force n exerted by the floor on the toes of one foot. A mechanical model of the situation is shown in Figure P8.24b, where T is the force exerted by the Achilles tendon on the foot and R is the force exerted by the tibia on the foot. Find the values of T, R, and when Fg = n = 700. N. Figure P8.24arrow_forwardThe Iron Cross When a gymnast weighing 750 N executes the iron cross as in Figure lN.91a, the primary muscles involved in supporting this position are the latissimus dorsi (lats") and the pectoralis major (pecs"). The rings exert an upward force on the aims and support the weight of the gymnast. The force exerted by the shoulder joint on the arm is labeled Fs, while the two muscles exert a total force Fw on the arm. Estimate the magnitude of the force Fw. Note that one ring supports half the weight of the gymnast, which is 375 N as indicated in Figure P8.91b. Assume that the force Fw acts at an angle of 45 below the horizontal at a distance of 4.0 cm from the shoulder joint In your estimate, take the distance from the shoulder joint to the hand to be L = 70 cm and ignore the weight of the arm.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_forward
- In an emergency situation, a person with a broken forearm ties a strap from his hand to clip on his shoulder as in Figure P8.92. His 1.60-kg forearm remains in a horizontal position and the strap makes an angle of = 50.0 with the horizontal. Assume the forearm is uniform, has a length of = 0.320 m, .assume the biceps muscle is relaxed, and ignore the mass and length of the hand. Find (a) the tension in the snap and (b) the components of the reaction force exerted by the humerus on the forearm. Figure P8.92arrow_forwardYou're carrying a 3.4-m-long, 24 kg pole to a construction site when you decide to stop for a rest. You place one end of the pole on a fence post and hold the other end of the pole 35 cm from its tip. How much force must you exert to keep the pole motionless in a horizontal position?arrow_forwardA beam resting on two pivots has a length of 6.00 m and mass 90.0 kg. The pivot under the left end exerts a normal force n1 on the beam, and the second pivot placed a distance 4.00 m from the left end exerts a normal force n2. A woman of mass 55.0 kg steps onto the left end of the beam and begins walking to the right as in Figure P8.22. The goal is to find the woman’s position when the beam begins to tip. Sketch a free-body diagram, labeling the gravitational and normal forces acting on the beam and placing the woman x meters to the right of the first pivot, which is the origin. Where is the woman when the normal force n1 is the greatest? What is n1 when the beam is about to tip? Use the force equation of equilibrium to find the value of n2 when the beam is about to tip. Using the result of part (c) and the torque equilibrium equation, with torques computed around the second pivot point, find the woman’s position when the beam is about to tip. Check the answer to part (e)…arrow_forward
- A 5.4 kgkg cat and a 2.5 kgkg bowl of tuna fish are at opposite ends of the 4.0-mm-long seesaw. How far to the left of the pivot must a 3.8 kgkg cat stand to keep the seesaw balanced?arrow_forwardFigure P8.29 shows a uniformbeam of mass m pivoted atits lower end, with a horizontalspring attached between its topend and a vertical wall. Thebeam makes an angle θ with thehorizontal. Find expressions for(a) the distance d the spring isstretched from equilibrium and(b) the components of the forceexerted by the pivot on thebeam.arrow_forward
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