Physics: Principles with Applications
7th Edition
ISBN: 9780321625922
Author: Douglas C. Giancoli
Publisher: Addison-Wesley
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Chapter 8, Problem 4Q
Why is it more difficult to do a sit-up with your hands behind your head than when your arms are stretched out in front of you? A diagram may help you to answer this.
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Consider an amusement park ride in which participants are rotated about a vertical axis in a cylinder with vertical walls. Once the angular velocity reaches its full value, the floor drops away and friction between the walls and the riders prevents them from sliding down. Construct a problem in which you calculate the necessary angular velocity that assures the riders will not slide down the wall. Include a free body diagram of a single rider. Among the variables to consider are the radius of the cylinder and the coefficients of friction between the riders’ clothing and the wall.
Chapter 8 Solutions
Physics: Principles with Applications
Ch. 8 - A solid ball and a solid cylinder roll down a...Ch. 8 - A bicycle odometer (which counts revolutions and...Ch. 8 - Prob. 2QCh. 8 - Prob. 3QCh. 8 - Why is it more difficult to do a sit-up with your...Ch. 8 - If the net force on a system is zero, is the net...Ch. 8 - Mammals that depend on being able to run fast have...Ch. 8 - This book has three symmetry axes through its...Ch. 8 - Can the mass of a rigid object be considered...Ch. 8 - The moment of inertia of a rotating solid disk...
Ch. 8 - Two inclines have the same height but make...Ch. 8 - Two spheres look identical and have the same mass....Ch. 8 - A sphere and a cylinder have the same radius and...Ch. 8 - Prob. 13QCh. 8 - Prob. 14QCh. 8 - 15. Can the diver of Fig. 8-28 do a somersault...Ch. 8 - When a motorcyclist leaves the ground on a jump...Ch. 8 - Prob. 17QCh. 8 - 18. The angular velocity of a wheel rotating on a...Ch. 8 - 19. In what direction is the Earth's angular...Ch. 8 - 20. ‘On the basis of the law of conservation of...Ch. 8 - Bonnie sits on the outer rim of a merry-go-round,...Ch. 8 - Prob. 2MCQCh. 8 - Prob. 3MCQCh. 8 - Prob. 4MCQCh. 8 - Prob. 5MCQCh. 8 - Prob. 6MCQCh. 8 - Prob. 7MCQCh. 8 - Prob. 8MCQCh. 8 - Prob. 9MCQCh. 8 - Prob. 10MCQCh. 8 - Prob. 11MCQCh. 8 - Prob. 12MCQCh. 8 - Suppose you are sitting on a rotating stool...Ch. 8 - Express the following angles in radians: (a)...Ch. 8 - The Sun subtends an angle of about 0.5° to us on...Ch. 8 - A laser beam is directed at the Moon, 380,000 km...Ch. 8 - The blades in a blender rotate at a rate of 6500...Ch. 8 - 5. (II) The platter of the hard drive of a...Ch. 8 - Prob. 6PCh. 8 - (a) A grinding wheel 0.35 m in diameter rotates at...Ch. 8 - Prob. 8PCh. 8 - Calculate the angular velocity (a) of a clock's...Ch. 8 - Prob. 10PCh. 8 - What is the linear speed, due to the Earth's...Ch. 8 - Prob. 12PCh. 8 - How fast (in rpm) must a centrifuge rotate ifa...Ch. 8 - Prob. 14PCh. 8 - Prob. 15PCh. 8 - Prob. 16PCh. 8 - An automobile engine slows down from 3500 rpm to...Ch. 8 - 18. (I) A centrifuge accelerates uniformly from...Ch. 8 - Prob. 19PCh. 8 - Prob. 20PCh. 8 - A wheel 31 cm in diameter accelerates uniformly...Ch. 8 - Prob. 22PCh. 8 - Prob. 23PCh. 8 - A 52-kg person riding a bike puts all her weight...Ch. 8 - Calculate the net torque about the axle of the...Ch. 8 - A person exerts a horizontal force of 42 N on the...Ch. 8 - Prob. 27PCh. 8 - The bolts on the cylinder head of an engine...Ch. 8 - Determine the net torque on the 2.0-m-long uniform...Ch. 8 - Determine the moment of inertia of a 10.8-kg...Ch. 8 - 31. (I) Estimate the moment of inertia of a...Ch. 8 - A merry-go-round accelerates from rest to 0.68...Ch. 8 - Prob. 33PCh. 8 - (II) A grinding wheel is a uniform cylinder with a...Ch. 8 - Prob. 35PCh. 8 - Prob. 36PCh. 8 - Prob. 37PCh. 8 - Prob. 38PCh. 8 - Prob. 39PCh. 8 - Prob. 40PCh. 8 - Prob. 41PCh. 8 - Prob. 42PCh. 8 - Prob. 43PCh. 8 - A centrifuge rotor rotating at 9200 rpm is shut...Ch. 8 - 45. (II) To get a flat, uniform cylindrical...Ch. 8 - 46. (Ill) Two blocks are connected by a light...Ch. 8 - 47 (III) An Atwood machine consists of two masses,...Ch. 8 - A hammer thrower accelerates the hammer (mass...Ch. 8 - 49. (I) An automobile engine develops a torque of...Ch. 8 - A centrifuge rotor has a moment of inertia of 325...Ch. 8 - Prob. 51PCh. 8 - Prob. 52PCh. 8 - Prob. 53PCh. 8 - Prob. 54PCh. 8 - Prob. 55PCh. 8 - Prob. 56PCh. 8 - Prob. 57PCh. 8 - Prob. 58PCh. 8 - Prob. 59PCh. 8 - What is the angular momentum of a 0.270-kg ball...Ch. 8 - (a) What is the angular momentum of a 2.8-kg...Ch. 8 - Prob. 62PCh. 8 - Prob. 63PCh. 8 - Prob. 64PCh. 8 - Prob. 65PCh. 8 - Prob. 66PCh. 8 - A person of mass 75 kg stands at the center of a...Ch. 8 - Prob. 68PCh. 8 - Prob. 69PCh. 8 - Prob. 70PCh. 8 - Prob. 71PCh. 8 - Prob. 72PCh. 8 - Prob. 73PCh. 8 - Prob. 74PCh. 8 - Prob. 75GPCh. 8 - Prob. 76GPCh. 8 - Prob. 77GPCh. 8 - Prob. 78GPCh. 8 - Prob. 79GPCh. 8 - Prob. 80GPCh. 8 - Prob. 81GPCh. 8 - Figure 8-59 illustrates an H20 molecule The O — H...Ch. 8 - A hollow cylinder (hoop) is rolling on a...Ch. 8 - Prob. 84GPCh. 8 - Prob. 85GPCh. 8 - Prob. 86GPCh. 8 - Prob. 87GPCh. 8 - Prob. 88GPCh. 8 - Prob. 89GPCh. 8 - Prob. 90GPCh. 8 - A large spool of rope rolls on the ground with the...Ch. 8 - The Moon orbits the Earth such that the same side...Ch. 8 - Prob. 93GPCh. 8 - Most of our Solar System's mass is contained in...Ch. 8 - Prob. 95GPCh. 8 - Prob. 96GP
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- Construct Your Own Problem Consider an amusement park ride in which participants are rotated about a vertical axis in a cylinder with vertical walls. Once the angular velocity reaches its full value, the floor drops away and friction between the walls and the riders prevents them from sliding down. Construct a problem in which you calculate the necessary angular velocity that assures the riders will not slide down the wall. Include a free body diagram of a single rider. Among the variables to consider are the radius of the cylinder and the coefficients of friction between the riders’ clothing and the wall.arrow_forwardimagine you are standing inside a fast moving bus. How do you position yourself to keep your balance?arrow_forwardCan you break down the buttom where it comes up with 63 degrees? How can I enter this into a calculator to get the correct answer?arrow_forward
- 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? (Try it yourself)arrow_forwardplease help me answer “why is it more difficult to lean over and push a heavy box across the floor than it is to attach a rope and pull the box at the same angle ? (give an explanation) question #3arrow_forwardConsider this: Both scenario has same length of surface of 60 meters. A. A 50-kg object is located exactly 30 meters from both side of the surface. B A 75-kg object is located 20 meters from the left edge of the surface. Compute the torque, draw a free body diagram and write a short description about it.arrow_forward
- A beam of mass M and length L is hanging from a rope perpendicular to a wall. The rope is attached at a point that is 75% of the length of the beam. A second rope is attached to the end of the beam. On the second rope hangs a block with mass m. (a) Draw all forces acting on the beam in a free body diagram. (b) Write the equations necessary for equilibrium in terms of the forces for this situation. (c) Use the torque equation to solve for the tension.arrow_forwardA 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_forwardOne end (A) of a thin rod rests on a floor, with coefficient of static friction μs. The other end (B) of the rod leans against a frictionless wall. The rod has a length of L and a mass of m. The rod has a uniform density, so the center-of-mass is a distance L/2 from either end. The rod does not move. variables only (m, g, L, θ, μs) a) Draw a free body diagram for the rod clearly showing all forces and where they are applied. Hint: There are four forces! b) On your diagram, draw and label the line of action and lever arm for the weight force about point A. c) What is the torque produced by the weight force about point A? d) Using static equilibrium equations, find the three support forces (two at A, one at B). e) Given the coefficient of static friction μs, what is the smallest possible angle before the rod starts to move?arrow_forward
- The 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_forwardPart of riding a bicycle involves leaning at the correct angle when making a turn, as seen below. To be stable, the force exerted by the ground must be on a line going through the center of gravity. The force on the bicycle wheel can be resolved into two perpendicular components—friction parallel to the road (this must supply the centripetal force) and the vertical normal force (which must equal the system’s weight). (a) Show that (as defined as shown) is related to the speed vand radius of curvature rof the turn in the same way as for an ideally banked roadway—that is, =tan1(v2/rg) . (b) Calculate for a 12.0-m/s turn of radius 30.0 m (as in a race).arrow_forward
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