4. Block A and spool B weigh 8 and 6 lb, respectively. The spool has a string wrapped around it to which a force P is applied. The coefficient of static friction between the spool and the contact surfaces at A and C is 0.25. Determine the value of P that causes impending motion, and determine if slip occurs at A, or C, or both locations simultaneously. D 6 in. 3 in.- B

4. Block A and spool B weigh 8 and 6 lb, respectively. The spool has a string wrapped around it to which a force P is applied. The coefficient of static friction between the spool and the contact surfaces at A and C is 0.25. Determine the value of P that causes impending motion, and determine if slip occurs at A, or C, or both locations simultaneously. D 6 in. 3 in.- B

University Physics Volume 1

18th Edition

ISBN:9781938168277

Author:William Moebs, Samuel J. Ling, Jeff Sanny

Publisher:William Moebs, Samuel J. Ling, Jeff Sanny

Chapter6: Applications Of Newton's Laws

Section: Chapter Questions

Problem 47P: (a) What is the maximum frictional force in the knee joint of a person who supports 66.0 kg of her...

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(a) What is the maximum frictional force in the knee joint of a person who supports 66.0 kg of her mass on that knee? (b) During strenuous exercise, it is possible to exert forces to the joints that are easily 10 times greater than the weight being supported. What is the maximum force of friction under such conditions? The frictional forces in joints are relatively small in all circumstances except when the joints deteriorate, such as from injury or arthritis. Increased frictional forces can cause further damage and pam.
A body of mass 100 kg is weighed at the North Pole and at the equator with a spring scale. What is the scale reading at these two points? Assume that g=9.83m/s2 at the pole.
Measuring coefficients of friction A coin is placed near one edge of a book lying on a table, and that edge of the book is lifted until the coin just slips down the incline as shown in Figure P4.82. The angle of the incline, C, called the critical angle, is measured. (a) Draw a free-body diagram for the coin when it is on the verge of slipping and identify all forces acting on it. Your free-body diagram should include a force of static friction acting up the incline. (b) Is the magnitude of the friction force equal to sn for angles less than C? Explain. What can you definitely say about the magnitude of the friction force for any angle c? (c) Show that the coefficient of static friction is given by s = tan c. (d) Once the coin starts to slide down the incline, the angle can be adjusted to a new value c c such that the coin moves down the incline with constant speed. How does observation enable you to obtain the coefficient of kinetic friction? Figure P4.82
(a) Give an example of different net external forces acting on the same system to produce different accelerations. (b) Give an example of the same net external force acting on systems of different masses, producing different accelerations. (c) What law accurately describes both effects? State it in words and as an equation.
A piece of bacon starts to slide down the pan when one side of a pan is raised up 5.0 cm. If the length of the pan from pivot to the raising point is 23.5 cm, what is the coefficient of static friction between the pan and the bacon?
A physics major is cooking breakfast when he notices that the frictional force between his steel spatula and his Teflon frying pan is only 0.200 N. Knowing the coefficient of kinetic friction between the two materials, he quickly calculates the normal force. What is it?
Consider the 52.0-kg mountain climber shown below. (a) Find the tension in the rope and the force that the mountain climber must exert with her feet on the vertical rock face to remain stationary. Assume that the force is exerted parallel to her legs. Also, assume negligible force exerted by her arms. (b) What is the minimum coefficient of friction between her shoes and the cliff?
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2. A block weighing 60N rest on a horizontal floor. What is the minimum force that will make the block move if the coefficient of static dfriction is 0.20? What is the minimum force that will keep the block moving at uniform speed once it starts moving if the coefficient of kinetic friction is 0.10?
A 392-N force parallel to the plane is required to support a body on an inclinedplane, of height 300 m and base 400 m. If the force exerted by the plane on thebody is 780N,a. what is the weight of the body?b. what is the frictional force between the
A Shopee delivery man named lan is dragging a trunk up the loading ramp of the delivery truck. The ramp has a slope angle of 20.0°, and lan pulls upward with a force (F) whose direction makes an angle of 30.0° with the ramp. a.) How large a force (F) is necessary for the component Fx parallel to the ramp be 75.ON? b.) How large will the component Fy perpendicular to the ramp be?
8. A block is at rest on a rough inclined plane and is connected to an object with the same mass as shown. The rope may be considered massless; and the pulley may be considered frictionless. The coeffi- cient of static friction between the block and the plane is us; and the coefficient of kinetic friction is k 0 A. g D. g - Hk sin(0) m a. What is the magnitude of the static frictional force acting on the block? B.m g [1 - sin(0)] C. mg D. mg cos(0) B. g - Hk cos(0) A. m g sin(0) E. mg [1 - cos(0)] b. If the rope were cut between the block and the pulley, what would be the magnitude of the acceleration of the block down the plane? C. g [sin(0) - μ cos(0)] sin(0)] c. If the mass of the suspended object is doubled, what will be the acceleration of the block up the plane? B. g [2 tan(0) - uk sin(0)] D. 2g [μ sin(0) - cos(0)] m E. g [tan (0) A. g [2 - μk sin(0)] C. g [2 cos(0) - μ sin(0)] E. g [2 sin(0) Hk Cos (0)]. -