Atwood Machine Special Cases An Atwood machine consists of two blocks (of masses and ) tied together with a massless rope that passes over a fixed, perfect (massless and frictionless) pulley. In this problem you'll investigate some special cases where physical variables describing the Atwood machine take on limiting values. Often, examining special cases will simplify a problem, so that the solution may be found from inspection or from the results of a problem you've already seen.For all parts of this problem, take upward to be the positive direction and take the gravitational constant, , to be positive. A Friction Experiment During an experiment, a crate is pulled along a rough horizontal surface by a constant force and the magnitude of the acceleration along the x direction, , is measured. The vector has a component along the x direction of magnitude . The experiment is repeated several times, with different values of each time. Friction Force on a Dancer on a Drawbridge A dancer is standing on one leg on a drawbridge that is about to open. The coefficients of static and kinetic friction between the drawbridge and the dancer's foot are and , respectively. represents the normal force exerted on the dancer by the bridge, and represents the gravitational force exerted on the dancer, as shown in the drawing . For all the questions, we can assume that the bridge is a perfectly flat surface and lacks the curvature characteristic of most bridges. A Modified Atwood Machine Consider the situation depicted in this applet. The red block moves along a rough surface. The system begins at rest. You may assume that the pulley and rope are both massless and frictionless. Problem 5.65 A block with mass is placed on an inclined plane with slope angle and is connected to a second hanging block that has mass by a cord passing over a small, frictionless pulley. The coefficient of static friction is and the coefficient of kinetic friction is . Problem 5.68 A window washer pushes his scrub brush up a vertical window at constant speed by applying a force as shown in the figure . The brush weighs 12.9 and the coefficient of kinetic friction is 0.200. Problem 5.83 Block A in the figure weighs 1.67 , and block B weighs 4.49 . The coefficient of kinetic friction between all surfaces is 0.22. A Ride on the Ferris Wheel A woman rides on a Ferris wheel of radius 16 that maintains the same speed throughout its motion. To better understand physics, she takes along a digital bathroom scale (with memory) and sits on it. When she gets off the ride, she uploads the scale readings to a computer and creates a graph of scale reading versus time. Note that the graph has a minimum value of 510 and a maximum value of 666 . Banked Frictionless Curve, and Flat Curve with Friction A car of mass = 1100 traveling at 45.0 enters a banked turn covered with ice. The road is banked at an angle , and there is no friction between the road and the car's tires. Short Answer Question - 5.4
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