Concept explainers
At a construction site, a 65.0-kg bucket of concrete hangs from a light (but strong) cable that passes over a light, friction-free pulley and is connected to an 80.0-kg box on a horizontal roof (Fig. P7.37). The cable pulls horizontally on the box, and a 50.0-kg bag of gravel rests on top of the box. The coefficients of friction between the box and roof are shown, (a) Find the friction force on the bag of gravel and on the box. (b) Suddenly a worker picks up the bag of gravel. Use energy conservation to find the speed of the bucket after it has descended 2.00 m from rest. (Use Newton’s laws to check your answer.)
Learn your wayIncludes step-by-step video
Chapter 7 Solutions
University Physics with Modern Physics Plus Mastering Physics with eText -- Access Card Package (14th Edition)
Additional Science Textbook Solutions
College Physics
Cosmic Perspective Fundamentals
Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
Sears And Zemansky's University Physics With Modern Physics
University Physics Volume 1
Glencoe Physical Science 2012 Student Edition (Glencoe Science) (McGraw-Hill Education)
- You are a bully. You pin a 48 kg dweeb to a wall so that his feet aren't touching the ground. Your arm is extended so that it makes an angle 28 degrees with the horizontal. The dweeb's back is so sweaty with fear that there is no friction between his back and the wall. What is the magnitude of the force , in N, you must apply to keep the dweeb in equilibrium? (Use g = 10 m/s2) This scenario is represented schematically below. Unfortunately for you, years later the dweeb is your boss and he makes your life miserable. (Please answer to the fourth decimal place - i.e 12.3445)arrow_forwardA 10 m long board that has a mass of 20 kg is held up by two vertical ropes. The left rope is 2 m from the left end of the board, and the other rope is 2 m from the right end of the board. A 40 kg box sits 2 m from the right end. Find the tension in the rope on the left.arrow_forwardStudents are performing an experiment with the setup shown above, where a block of mass M sits on a horizontal table. The coefficient of kinetic friction between the block and the table is uk. The block is connected to a hanging object over a pulley. The pulley has negligible mass and friction. The string connecting the two is very light and does not stretch. The students add mass to the hanging object so that its mass is mm, where m < M, and the block-hanging object system is released from rest. The hanging object falls for a distance h, at which point it collides with the ground and comes to rest. The block on the table keeps sliding and travels a total distance d before coming to rest. It does not reach the pulley, and d > h. If the experiment were repeated where the height hh above the floor was increased, would the distance that the block slides after the hanging object hits the floor increase, decrease, or remain the same? Justify your answer without using or manipulating…arrow_forward
- A 5 kg box rests on a tabletop. On one side, it compresses a spring with a stiffness of 1000 N/m by 1 cm. If the friction force cancels out the force of the spring what must be the minimum coefficient of static friction between the box and table to keep the box from moving?arrow_forwardA 200 g hockey puck is launched up a metal ramp that is inclined at a 30° angle. The coefficients of static and kinetic friction between the hockey puck and the metal ramp are us 0.40 and uk = 0.30, respectively. The puck's initial speed is 4.9 m/s. What speed does it have when it slides back down to its starting point? 2.8 m/s 4.9 m/s 4.2 m/s 3.5 m/sarrow_forwardA stone has a mass of 8.79 g and is wedged into the tread of an automobile tire, as the drawing shows. The coefficient of static friction between the stone and each side of the tread channel is 0.818. When the tire surface is rotating at 10.9m/s, the stone flies out the tread. The magnitude FN of the normal force that each side of the tread channel exerts on the stone is 2.46 N. Assume that only static friction supplies the centripetal force, and determines the radius r of the tire (in terms of m)arrow_forward
- In the back of the truck is a 200kg box that has a coefficient of static friction of 0.8 and a coefficient of kinetic friction of 0.4 between the truck and the box. You are driving on the freeway at 25m/s. There is a car ahead of you that is driving at 30m/s. Your front bumper is 30m behind the back of the first car. You would like to pass the other car and pull back into the same lane when your back bumper is 10m ahead of the front bumper of the first car in 5 seconds. The length of the car ahead of you is 3m and the length of your car is 4m.a) What minimum acceleration do you need to do this?b) What distance does your car travel in that time?c) Does the box in your truck start to slide off the truck?arrow_forwardAn 80.0 kg mail bag hangs by a vertical rope 3.7 m long. A postal worker then displaces the bag to a position 2.5 meters sideways from its original position, always keeping the rope taut. What horizontal force is necessary to hold the bag in the new position?arrow_forwardA 400 g block with an initial speed of 80 cm/s slides along a horizontal tabletop against a friction force of 0.70N. (a) How far will it slide before stopping? (b) What is the coefficient of friction between the block and the tabletop?arrow_forward
- A 5.0 g coin is placed 15 cm from the center of a turntable. The coin has static and kinetic coefficients of friction with the turntable surface of μs = 0.70 and μk = 0.50. The turntable very slowly speeds up. What is the frequency of the rotation of the turntable expressed in revolutions per minute when the coin slides off? Express your answer in revolutions per minute.arrow_forwardA 2.00-kg block is at rest on a horizontal plank that is 1.50 m long. When one end of the plane is raised to 0.50 m, the block starts sliding down. What is the coefficient of static/starting friction between the block and the plank? O 0.43 O 0.35 0.33 O 0.53arrow_forwardAn aluminum block is placed at rest on an inclined plane that is made of steel. Once released, the block remains at rest on the incline. The coefficients of static and kinetic friction between aluminum and steel are 0.61 and 0.47 respectively. The aluminum block has a mass of 3.45 kg and the incline makes an angle of 12.5° relative to the horizontal. What is the magnitude of the static frictional force between the block and incline?arrow_forward
- Glencoe Physics: Principles and Problems, Student...PhysicsISBN:9780078807213Author:Paul W. ZitzewitzPublisher:Glencoe/McGraw-HillPrinciples of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning