Phys. Chapter 08 - Beau Chene High School Home Page

51. A uniform ladder 8.00 m long and weighing 200.0 Nrests against a smooth wall. The coefficient of staticfriction between the ladder and the ground is 0.600,and the ladder makes a 50.0° angle with the ground.How far up the ladder can an 800.0 N person climbbefore the ladder begins to slip?52. A 0.0200 m diameter coin rolls up a 15.0° inclinedplane. The coin starts with an initial angular speedof 45.0 rad/s and rolls in a straight line without slipping.How much vertical distance does it gainbefore it stops rolling?53. In a circus performance, a large 4.0 kg hoop with aradius of 2.0 m rolls without slipping. If the hoop isgiven an angular speed of 6.0 rad/s while rolling onthe horizontal and is allowed to roll up a rampinclined at 15° with the horizontal, how far (measuredalong the incline) does the hoop roll?54. A 12 kg mass is attached to a cord that is wrappedaround a wheel with a radius of 10.0 cm, as shown inFigure 8-24. The acceleration of the mass down thefrictionless incline is measured to be 2.0 m/s 2 .Assumingthe axle of the wheel to be frictionless, determinea. the force in the rope.b. the moment of inertia of the wheel.c. the angular speed of the wheel 2.0 s after itbegins rotating, starting from rest.2.0 m/s 212 18 kg cm37°Figure 8-2455. A person is standing on tiptoe, and the person’stotal weight is supported by the force on the toe. Amechanical model for the situation is shown in Figure8-25, where T is the force in the Achilles tendonand R is the force on the foot due to the tibia.Assume the total weight is 700.0 N, and find the valuesof T and R, if the angle labeled q is 21.2°.rF nθ T15.0° R 90.0°18.0 cm25.0 cmFigure 8-2556. A cylindrical fishing reel has a mass of 0.85 kg and aradius of 4.0 cm. A friction clutch in the reel exerts arestraining torque of 1.3 N •m if a fish pulls on theline. The fisherman gets a bite, and the reel beginsto spin with an angular acceleration of 66 rad/s 2 .Find the following:a. the force of the fish on the lineb. the amount of line that unwinds from the reelin 0.50 s57. The combination of an applied force and a frictionalforce produces a constant torque of 36 N • m on awheel rotating about a fixed axis. The applied forceacts for 6.0 s, during which time the angular speedof the wheel increases from 0 to 12 rad/s. Theapplied force is then removed, and the wheel comesto rest in 65 s. Answer the following questions:a. What is the moment of inertia of the wheel?b. What is the frictional torque?c. How many revolutions does the wheel makeduring the entire 71 s time interval?58. A cable passes over a pulley. Because of friction, theforce in the cable is not the same on opposite sides ofthe pulley. The force on one side is 120.0 N, and theforce on the other side is 100.0 N. Assuming that thepulley is a uniform disk with a mass of 2.1 kg and aradius of 0.81 m, determine the angular accelerationof the pulley.59. As part of a kinetic sculpture, a 5.0 kg hoop with aradius of 3.0 m rolls without slipping. If the hoop isgiven an angular speed of 3.0 rad/s while rolling onthe horizontal and then rolls up a ramp inclined at20.0° with the horizontal, how far does the hooproll along the incline?Copyright © by Holt, Rinehart and Winston. All rights reserved.Rotational Equilibrium and Dynamics309