Concept explainers
** Demolition An old building is being demolished by swinging a heavy metal ball from a crane. Suppose that the 100-kg ball swings from a 20-m-long wire at speed 16 m/s as the wire passes the vertical orientation. (a) What tension force must the wire be able to withstand in order not to break? (b) Assume the ball stops after sinking 1.5 m into the wall of the building. What was the average force that the ball exerted on the wall? Indicate any assumptions you made for each part of the problem.
Trending nowThis is a popular solution!
Chapter 5 Solutions
College Physics
Additional Science Textbook Solutions
University Physics (14th Edition)
College Physics: A Strategic Approach (4th Edition)
Essential University Physics: Volume 2 (3rd Edition)
Introduction to Electrodynamics
Cosmic Perspective Fundamentals
Applied Physics (11th Edition)
- In a laboratory model of cars skidding to a stop, data are measured for four trials using two blocks. The blocks have identical masses but different coefficients of kinetic friction with a table: k = 0.2 and 0.8. Each block is launched with speed vi = 1 m/s and slides across the level table as the block comes to rest. This process represents the first two trials. For the next two trials, the procedure is repeated but the blocks are launched with speed vi = 2 m/s. Rank the four trials (a) through (d) according to the stopping distance from largest to smallest. If the stopping distance is the same in two cases, give them equal rank. (a) vi = 1 m/s, = 0.2 (b) vi = 1 m/s, k = 0.8 (c) vi = 2 m/s, = 0.2 (d) vi =2 m/s, k = 0.8arrow_forwardReview. A force platform is a tool used to analyze the performance of athletes by measuring the vertical force the athlete exerts on the ground as a function of time. Starting from rest, a 65.0-kg athlete jumps down onto the platform from a height of 0.600 m. While she is in contact with the platform during the time interval 0t 0.800 s, the force she exerts on it is described by the function F = 9 200t 11 500 t2 where F is in newtons and t is in seconds. (a) What impulse did the athlete receive from the platform? (b) With what speed did she reach the platform? (c) With what speed did she leave it? (d) To what height did she jump upon leaving the platform?arrow_forwardIn a laboratory model of cars skidding to a stop, data are measured for four trials using two blocks. The blocks have identical masses but different coefficients of kinetic friction with a table: k = 0.2 and 0.8. Each block is launched with speed vi = 1 m/s and slides across the level table as the block comes to rest. This process represents the first two trials. For the next two trials, the procedure is repeated but the blocks are launched with speed vi = 2 m/s. Rank the four trials (a) through (d) according to the stopping distance from largest to smallest. If the stopping distance is the same in two cases, give them equal rank. (a) vi = 1 m/s, k = 0.2 (b) vi = 1 m/s, k = 0.8 (c) vi = 2 m/s, k = 0.2 (d) vi = 2 m/s, k = 0.8arrow_forward
- You have a new internship, where you are helping to design a new freight yard for the train station in your city. There will be a number of dead-end sidings where single cars can be stored until they are needed. To keep the cars from running off the tracks at the end of the siding, you have designed a combination of two coiled springs as illustrated in Figure P7.41. When a car moves to the right in the figure and strikes the springs, they exert a force to the left on the car to slow it down. Both springs are described by Hookes law and have spring constants k1 = 1 600 N/m and k2 = 3 400 N/m. After the first spring compresses by a distance of d = 30.0 cm, the second spring acts with the first to increase the force to the left on the car in Figure P7.41. When the spring with spring constant k2 compresses by 50.0 cm, the coils of both springs are pressed together, so that the springs can no longer compress. A typical car on the siding has a mass of 6 000 kg. When you present your design to your supervisor, he asks you for the maximum speed that a car can have and be stopped by your device. Figure P7.41arrow_forwardA roller-coaster car (Fig. P6.16) has a mass of 500 kg when fully loaded with passengers. The path of the ca coaster from its initial point shown in the figure to point involves only up-and-down motion (as seen by the riders), with no motion to the left or right, (a) If the vehicle has a speed of 20.0 m/s at point . what is the force exerted by the track on the car at this point? (b) What is the maximum speed the vehicle can have at point and still remain on the track? Assume the roller-coaster tracks at points andl are parts of vertical circles of radius r1 = 10.0 m and i2 = 15.0 m, respectively.arrow_forwardA skier starts at rest at the top of a large hemispherical hill (Fig. P7.63). Neglecting friction, show that the skier will leave the hill and become airborne at a distance h = R/3 below the top of the hill. Hint: At this point, the normal force goes to zero. Figure P7.63arrow_forward
- Chris, a recent physics major, wanted to design and carry out an experiment to show that an objects mass determines its inertia. He used an ultrasound device to measure acceleration of a low-friction cart attached to a hanging block to provide the same force on the cart during each run (Fig. P6.76A). Chris varied the mass of the cart by varying the number of lead rods placed in it. Chris used Newtons second law Fx=FT=Max to predict his results. He reasoned that because FT is the same for each run, the carts acceleration should be inversely proportional to its mass: ax=FTM=constantM(1) Chriss goal was to show that his data fit Equation (1). He decided to analyze his results by plotting ax as a function of 1/M; Equation (1) predicted that he should get a straight line, passing through the origin with a slope equal to the tension (red line in Fig. P6.76B): Chris ran several trials for each run, averaged his results and estimated the error. He then plotted his data (green line in Fig. P6.76B). Chris was excited to see that he correctly predicted that the data fell along a straight line: ax=(0.27N)1M(0.048m/s2) According to the straight-line fit to the data, the slope of the line is 0.27 N, which was close to the weight of the hanging mass and therefore close to the tension in the string. Chris, though, was disappointed to see that the line had a negative intercept. Mathematically, as M, 1M0. Chris was confused because he believed that as the mass increased, the carts acceleration should approach zero. He was quite sure that he did not discover some new property of inertia or mass. After convincing himself that he was not being careless in the laboratory and that his data were correct, he started to search for an explanation for the discrepancy between his prediction and his data. Help Chris find an explanation. FIGURE P6.76 A. Chriss experimental apparatus. B. Chriss prediction (red line) and experimental results (green line).arrow_forwardAn athlete grips a light rope that passes over a low-friction pulley attached to tire ceiling of a gym. A sack of sand precisely equal in weight to the athlete is tied to the other end of the rope. Both the sand and the athlete are initially at rest. The athlete climbs the rope, sometimes speeding up and slowing down as he does so. What happens to the sack of sand? Explain.arrow_forwardA car is moving forward slowly and is speeding up. A student claims that the car exerts a force on itself or that the cars engine exerts a force on the car. (a) Argue that this idea cannot be accurate and that friction exerted by the road is the propulsive force on the car. Make your evidence and reasoning as persuasive as possible. (b) Is it static or kinetic friction? Suggestions: Consider a road covered with light gravel. Consider a sharp print of the tire tread on an asphalt road, obtained by coating the tread with dust.arrow_forward
- Review. A student, along with her backpack on the floor next to her, is in an elevator that is accelerating upward with acceleration a. The student gives her backpack a quick kick at t = 0, imparting to it speed v and causing it to slide across the elevator floor. At time t, the backpack hits the opposite wall a distance L away from the student. Find the coefficient of kinetic friction k between the backpack and the elevator floor.arrow_forwardA fisherman poles a boat as he searches for his next catch. He pushes parallel to the length of the light pole, exerting a force of 240 N on the bottom of a shallow lake. The pole lies in the vertical plane containing the boats keel. At one moment, the pole makes an angle of 35.0 with the vertical and the water exerts a horizontal drag force of 47.5 N on the boat, opposite to its forward velocity of magnitude 0.857 m/s. The mass of the boat including its cargo and the worker is 370 kg. (a) The water exerts a buoyant force vertically upward on the boat. Find the magnitude of this force. (b) Assume the forces are constant user a short interval of time. Find the velocity of the boat 0.450 s after the moment described, (c) If the angle of the pole with respect to the vertical increased but the exerted force against the bottom remained the same, what would happen to buoyant forte and the acceleration of the boat?arrow_forwardIf you push a box across the floor its "physics work" but if you push on the wall it's not. Which of the following choices best explains why? Question 12 options: The direction of the force on the box is not the same direction as the motion. You're applying a force to the box but you are not applying a force to the wall. You're not applying a force to the box but you are applying a force to the wall. The box is moving but the wall is not.arrow_forward
- Physics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPrinciples of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningClassical Dynamics of Particles and SystemsPhysicsISBN:9780534408961Author:Stephen T. Thornton, Jerry B. MarionPublisher:Cengage Learning
- College PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningPhysics for Scientists and EngineersPhysicsISBN:9781337553278Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning