Essential University Physics: Volume 1 (3rd Edition)
3rd Edition
ISBN: 9780321993724
Author: Richard Wolfson
Publisher: PEARSON
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Textbook Question
Chapter 6, Problem 3FTD
Must you do work to whirl a ball around on the end of a string Explain.
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Chapter 6 Solutions
Essential University Physics: Volume 1 (3rd Edition)
Ch. 6.2 - Two objects are each displaced the same distance,...Ch. 6.3 - Three forces have magnitudes in newtons that are...Ch. 6.4 - For each situation, tell whether the net work done...Ch. 6 - Give two examples of situations in which you might...Ch. 6 - If the scalar product of two nonzero vectors is...Ch. 6 - Must you do work to whirl a ball around on the end...Ch. 6 - If you pick up a suitcase and put it down, how...Ch. 6 - You want to raise a piano a given height using a...Ch. 6 - Does the gravitational force of the Sun do work on...Ch. 6 - A pendulum bob swings back and forth on the end of...
Ch. 6 - Does your cars kinetic energy change if you drive...Ch. 6 - A watt-second is a unit of what quantity? Relate...Ch. 6 - A truck is moving northward at 55 mi/h. Later, its...Ch. 6 - Is it possible for you to do work on an object...Ch. 6 - How much work do you do as you exert a 75-N force...Ch. 6 - If the coefficient of kinetic friction is 0.21,...Ch. 6 - A crane lifts a 650-kg beam vertically upward 23 m...Ch. 6 - The worlds highest waterfall, the Cherun-Meru in...Ch. 6 - A meteorite plunges to Earth, embedding itself 75...Ch. 6 - An elevator of mass m rises a vertical distance h...Ch. 6 - Prob. 19ECh. 6 - Find the work done by a force F = 1.8 + 2.2 N as...Ch. 6 - To push a stalled car, you apply a 470-N force at...Ch. 6 - Find the total work done by the force shown in...Ch. 6 - How much work does it take to stretch a spring...Ch. 6 - Uncompressed, the spring for an automobile...Ch. 6 - You do 8.5 J of work to stretch a spring with k =...Ch. 6 - Spider silk is a remarkable elastic material. A...Ch. 6 - Whats the kinetic energy of a 2.4105-kg airplane...Ch. 6 - Prob. 28ECh. 6 - At what speed must a 950-kg subcompact car be...Ch. 6 - A 60-kg skateboarder comes over the top of a hill...Ch. 6 - After a tornado, a 0.50-g drinking straw was found...Ch. 6 - From what height would you have to drop a car for...Ch. 6 - A typical human diet is 2000 calories per day,...Ch. 6 - A horse plows a 200-m-long furrow in 5.0 min,...Ch. 6 - A typical car battery stores about 1 kWh of...Ch. 6 - A sprinter completes a 100-m dash in 10.6 s. doing...Ch. 6 - How much work can a 3.5-hp lawnmower engine do in...Ch. 6 - A 75-kg long-jumper takes 3.1 s to reach a prejump...Ch. 6 - Estimate your power output as you do deep knee...Ch. 6 - In midday sunshine, solar energy strikes Earth at...Ch. 6 - It takes about 20 kJ to melt an ice cube. A...Ch. 6 - Prob. 42ECh. 6 - You slide a box of books at constant speed up a 30...Ch. 6 - Two people push a stalled car at its front doors,...Ch. 6 - Youre at the gym, doing arm raises. With each rep....Ch. 6 - A locomotive does 7.9 1011 J of work in pulling a...Ch. 6 - You pull a box 23 in horizontally, using the rope...Ch. 6 - Prob. 48PCh. 6 - (a) Find the scalar product of the vectors a + b...Ch. 6 - Looking to cut costs, the airline you work for...Ch. 6 - How much work does a force F = 67 + 23 + 55k N do...Ch. 6 - A force F Facts in the x-direction, its magnitude...Ch. 6 - A certain amount of work is required to stretch...Ch. 6 - A force with magnitude F = a x acts in the...Ch. 6 - The force exerted by a rubber band is given...Ch. 6 - You put your little sister (mass m) on a swing...Ch. 6 - Two unknown elementary particles pass through a...Ch. 6 - A tractor tows a plane from its airport gate,...Ch. 6 - E. coli bacteria swim by means of flagella that...Ch. 6 - On February 15, 2013, an asteroid moving at 19...Ch. 6 - An elevator ascends from the ground floor to the...Ch. 6 - Youre asked to assess the reliability of a nuclear...Ch. 6 - A force pointing in the x-direction is given by F...Ch. 6 - A force pointing in the x-direction is given by F...Ch. 6 - Two vectors have equal magnitude, and their scalar...Ch. 6 - At what rate can a half-horsepower well pump...Ch. 6 - The rate at which the United States imports oil,...Ch. 6 - By measuring oxygen uptake, sports physiologists...Ch. 6 - Youre writing performance specifications for a new...Ch. 6 - A 1400-kg car ascends a mountain road at a steady...Ch. 6 - You do 2.2 kJ of work pushing a 78-kg trunk at...Ch. 6 - (a) Find the work done in lifting 1 L of blood...Ch. 6 - (a) What power is needed to push a 95-kg crate at...Ch. 6 - You mix flour into bread dough, exerting a 45-N...Ch. 6 - A machine does work at a rate given by P = ct2,...Ch. 6 - A typical bumblebee has mass 0.25 mg. It beats its...Ch. 6 - Youre trying to decide whether to buy an...Ch. 6 - Your friend does five reps with a barbell, on each...Ch. 6 - A machine delivers power at a decreasing rate P =...Ch. 6 - A locomotive accelerates a freight train of total...Ch. 6 - A force given by F = b/x acts in the x-direction,...Ch. 6 - Youre assisting a cardiologist in planning a...Ch. 6 - Youre an engineer for a company that makes...Ch. 6 - You push an object of mass m slowly, partway up a...Ch. 6 - A particle moves from the origin to the point x =...Ch. 6 - Repeat Problem 85 for the following cases: (a) the...Ch. 6 - The worlds fastest elevator, in Taiwans Taipei 101...Ch. 6 - An experimental measurement of the force required...Ch. 6 - Youre an expert witness in a medical malpractice...Ch. 6 - The energy in a batted baseball comes from the...Ch. 6 - The energy in a batted baseball comes from the...Ch. 6 - The energy in a batted baseball comes from the...Ch. 6 - The energy in a batted baseball comes from the...
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- A 40.0-kg child swings in a swing supported by two chains, each 3.00 m long. The tension in each chain at the lowest point is 350 N. Find (a) the childs speed at the lowest point and (b) the force exerted by the seat on the child at the lowest point. (Ignore the mass of the seat.)arrow_forwardIntegrated Concepts Riders in an amusement park ride shaped like a Viking ship hung from a large pivot are rotated back and forth like a rigid pendulum. Sometime near the middle of the ride, the ship is momentarily motionless at the top of its circular arc. The ship then swings down under the influence of gravity. (a) Assuming negligible friction, find the speed of the riders at the bottom of its arc, given the system's center of mass travels in an arc having a radius of 14.0 m and the riders are near the center of mass. (b) What is the centripetal acceleration at the bottom of the arc? (c) Draw a free body diagram of the forces acting on a rider at the bottom of the arc. (d) Find the force exerted by the ride on a 60.0 kg rider and compare it to her weight. (e) Discuss whether the answer seems reasonable.arrow_forwardA childs toy consists of a small wedge that has an acute angle (Fig. P6.28). The sloping side of the wedge is frictionless, and an object of mass m on it remains at constant height if the wedge is spun at a certain constant speed. The wedge is spun by rotating, as an axis, a vertical rod that is firmly attached to the wedge at the bottom end. Show that, when the object sits at rest at a point at distance L up along the wedge, the speed of the object must be v = (gL sin )1/2. Figure P6.28arrow_forward
- An athlete in a gym applies a constant force of 50 N to the pedals of a bicycle to keep the rotation rate of the wheel at 10 rev/s. The length of the pedal arms is 30 cm. What is the power delivered to the bicycle by the athlete?arrow_forwardThe second power of the distance from the inertia axis to an element of area is used to calculate the: a)Area of an object. b)Gravitational potential energy of an object. c)Centroid of an object. d)Second moment of area or moment of inertia of an object.arrow_forwardA block of mass m1 = 20.0 kg is connected to a block of mass m2 = 30.0 kg by a massless string that passes over a light, frictionless pulley. The 30.0-kg block is connected to a spring that has negligible mass and a force constant of k = 250 N/m as shown in Figure P7.73. The spring is un-stretched when the system is as shown in the figure, and the incline is frictionless. The 20.0-kg block is pulled a distance h = 20.0 cm down the incline of angle = 40.0 (so that the 30.0-kg block is 40.0 cm above the floor) and released from rest. Find the speed of each block when the 30.0-kg block is 20.0 cm above the floor (that is, when the spring is unstretched). Figure P7.73arrow_forward
- Unreasonable Results A mother pushes her child on a swing so that his speed is 9.00 m/s at the lowest point of his path. The swing is suspended 2.00 m above the child's center of mass. (a) What is the magnitude of the centripetal acceleration of the child at the low point? (b) What is the magnitude of the force the child exerts on the seat if his mass is 18.0 kg? (c) What is unreasonable about these results? (d) Which premises are unreasonable or inconsistent?arrow_forwardA cord is wrapped around a pulley that is shaped like a disk of mass m and radius r. The cords free end is connected to a block of mass M. The block starts from rest and then slides down an incline that makes an angle with the horizontal as show n in Figure P10.48. The coefficient of kinetic friction between block and incline is . (a) Use energy methods to show that the blocks speed as a function of position d down the incline is v=4Mgd(sincos)m+2M (b) Find the magnitude of the acceleration of the block in terms of , m, M, g, and . Figure P10.48arrow_forwardReview. Why is the following situation impossible? An athlete tests her hand strength by having an assistant hang weights from her belt as she hangs onto a horizontal bar with her hands. When the weights hanging on her belt have increased to 80% of her body weight, her hands can no longer support her and she drops to the floor. Frustrated at not meeting her hand-strength goal, she decides to swing on a trapeze. The trapeze consists of a bar suspended by two parallel ropes, each of length , allowing performers to swing in a vertical circular are (Fig. P8.38). The athlete holds the bar and steps off an elevated platform, starting from rest with the ropes at an angle i = 60.0 with respect to the vertical. As she swings several times back and forth in a circular are, she forgets her frustration related to the hand-strength test. Assume the size of the performers body is small compared to the length and air resistance is negligible. Figure P8.38arrow_forward
- An open box slides across a frictionless, icy surface of a frozen lake. What happens to the speed of the box as water from a rain shower falls vertically downward into the box? Explain.arrow_forwardA light rod of length 2L is free to rotate in a vertical plane about a frictionless pivot through its center. A particle of mass m1 is attached at one end of the rod, and a mass m2 is at the opposite end, where m1 m2. The system is released from rest in the vertical position shown in Figure P8.84a, and at some later time, the system is rotating in the Position shown in Figure P8.84b. Take the reference point of the gravitational potential energy to be at the pivot, (a) Find an expression for the system's total mechanical energy in the vertical position. (b) Find an expression for the total mechanical energy in the rotated position shown in Figure P8.84b. (c) Using the fact that the mechanical energy of the system is conserved, how would you determine the angular speed co of the system in the rotated position? (d) Find the magnitude of the torque on the system in the vertical position and in the routed position. Is the torque constant? Explain what these results imply regarding the angular momentum of the system, (c) Find an expression for the magnitude of the angular acceleration of the system in the rotated position. Does your result make sense when the rod is horizontal? When it is vertical? Explain. Figure P8.84arrow_forward
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Mechanical work done (GCSE Physics); Author: Dr de Bruin's Classroom;https://www.youtube.com/watch?v=OapgRhYDMvw;License: Standard YouTube License, CC-BY