Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)
4th Edition
ISBN: 9780133942651
Author: Randall D. Knight (Professor Emeritus)
Publisher: PEARSON
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Chapter 8, Problem 55EAP
The physics of circular motion sets an upper limit to the speed of human walking. (If you need to go faster, your gait changes from a walk to a run.) If you take a few steps and watch what’s happening, you’ll see that your body pivots in circular motion over your forward foot as you bring your rear foot forward for the next step. As you do so, the normal force of the ground on your foot decreases and your body tries to “lift off’ from the ground.
a. A person’s center of mass is very near the hips, at the top of the legs. Model a person as a particle of mass m at the top of a leg of length L. Find an expression for the person’s maximum walking speed vmax.
b. Evaluate your expression for the maximum walking speed of a 70 kg person with a typical leg length of 70 cm. Give your answer in both m/s and mph, then comment, based on your experience, as to whether this is a reasonable result. A “normal” walking speed is about 3 mph.
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Chapter 8 Solutions
Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)
Ch. 8 - In uniform circular motion, which of the following...Ch. 8 - A car runs out of gas while driving down a hill....Ch. 8 - FIGURE Q8.3 is a bird's-eye view of particles on...Ch. 8 - Tarzan swings through the jungle on a massless...Ch. 8 - FIGURE Q8.5 shows two balls of equal mass moving...Ch. 8 - Ramon and Sally are observing a toy car speed up...Ch. 8 - A jet plane is flying on a level course at...Ch. 8 - A small projectile is launched parallel to the...Ch. 8 - 9. You can swing a ball on a string in a vertical...Ch. 8 - A golfer starts with the club over her head and...
Ch. 8 - As a science fair project, you want to launch an...Ch. 8 - A 500 g model rocket is on a cart that is rolling...Ch. 8 - A 4.0 × 1010 kg asteroid is heading directly...Ch. 8 - A 55 kg astronaut who weighs 180 N on a distant...Ch. 8 - A 1500 kg car drives around a flat 200-m-diameter...Ch. 8 - A 1500 kg car takes a 50-m-radius unbanked curve...Ch. 8 - A 200 g block on a 50-cm-long string swings in a...Ch. 8 - In the Bohr model of the hydrogen atom, an...Ch. 8 - Suppose the moon were held in its orbit not by...Ch. 8 - 10. A highway curve of radius 500 m is designed...Ch. 8 - It is proposed that future space stations create...Ch. 8 - A 5.0 g coin is placed 15 cm from the center of a...Ch. 8 - Mass m1on the frictionless table of FIGURE EX8.13...Ch. 8 - A satellite orbiting the moon very near the...Ch. 8 - What is free-fall acceleration toward the sun at...Ch. 8 - 16. A 9.4 × 1021 kg moon orbits a distant planet...Ch. 8 - Communications satellites are placed in circular...Ch. 8 - A car drives over the top of a hill that has a...Ch. 8 - The weight of passengers on a roller coaster...Ch. 8 - A roller coaster car crosses the top of a circular...Ch. 8 - The normal force equals the magnitude of the...Ch. 8 - A student has 65-cm-long arms. What is the minimum...Ch. 8 - While at the county fair, you decide to ride the...Ch. 8 - A 500 g ball swings in a vertical circle at the...Ch. 8 - A 500 g ball moves in a vertical circle on a...Ch. 8 - A heavy ball with a weight of 100 N (m = 10.2 kg)...Ch. 8 - A toy train rolls around a horizontal...Ch. 8 - 28. A new car is tested on a 200-m-diameter track....Ch. 8 - An 85,000 kg stunt plane performs a loop-the-loop,...Ch. 8 - Three cars are driving at 25 m/s along the road...Ch. 8 - Derive Equations 8.3 for the acceleration of a...Ch. 8 - 32. A 100 g bead slides along a frictionless wire...Ch. 8 - 33. Space scientists have a large test chamber...Ch. 8 - 34. A 5000 kg interceptor rocket is launched at an...Ch. 8 - Prob. 35EAPCh. 8 - 36. A rocket- powered hockey puck has a thrust of...Ch. 8 - Prob. 37EAPCh. 8 - A 2.0 kg projectile with initial velocity m/s...Ch. 8 - A 75 kg man weighs himself at the north pole and...Ch. 8 - A concrete highway curve of radius 70 m banked at...Ch. 8 - a. an object of mass m swings in horizontal circle...Ch. 8 -
42. You’ve taken your neighbor’s young child to...Ch. 8 - A 4.4-cm-diameter, 24 g plastic ball is attached...Ch. 8 - A charged particle of mass m moving with speed v...Ch. 8 - Two wires are tied to the 2.0 kg sphere shown in...Ch. 8 - Two wires are tied to the 300 g sphere shown in...Ch. 8 - A conical pendulum is formed by attaching a ball...Ch. 8 - The 10 mg bead in FIGURE P8.48 is free to slide on...Ch. 8 - In an old-fashioned amusement park ride,...Ch. 8 - The ultracentrifuge is an important tool for...Ch. 8 - In an amusement park ride called The Roundup,...Ch. 8 - 52. Suppose you swing a ball of mass m in a...Ch. 8 - A 30 g ball rolls around a 40-cm-diameter L-shaped...Ch. 8 - FIGURE P8.54 shows a small block of mass m sliding...Ch. 8 - The physics of circular motion sets an upper limit...Ch. 8 - A 100 g ball on a 60-cm-long string is swung in a...Ch. 8 - A 60 g ball is tied to the end of a 50-cm-long...Ch. 8 - Elm Street has a pronounced dip at the bottom of a...Ch. 8 - 59. A 100 g ball on a 60-cm-long string is swung...Ch. 8 - Scientists design a new particle accelerator in...Ch. 8 - 61. A 1500 kg car starts from rest and drives...Ch. 8 - Prob. 62EAPCh. 8 - 63. A 2.0 kg ball swings in a vertical circle on...Ch. 8 - In Problems 64 and 65 you are given the equation...Ch. 8 - In Problems 64 and 65 you are given the equation...Ch. 8 - Sam (75 kg) takes off up a 50-m-high, 10°...Ch. 8 - In the absence of air resistance, a projectile...Ch. 8 - The father of Example 8.2 stands at the summit of...Ch. 8 - A small bead slides around a horizontal circle at...Ch. 8 - A 500 g steel block rotates on a steel table while...Ch. 8 - If a vertical cylinder of water (or any other...
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