Temas Variados / Problemas Resueltos Fisica Libro E. Tippens

Problemas Resueltos Fisica Libro E. Tippens

Trabajos Documentales: Problemas Resueltos Fisica Libro E. Tippens
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Enviado por:  Albert  17 marzo 2011
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[pic]; Fc = 2630 N, No

10-10. An 8-lb object swings in horizontal circle with a speed of 95 ft/s. What is the radius of the path, if the centripetal force is 2000 lb?

[pic]

[pic]; R = 1.13 ft

*10-11. Two 8-kg masses are attached to the end of a tin rod 400 mm long. The rod is supported in the middle and whirled in a circle. The rod can support a maximum tension of only 800 N. What is the maximum frequency of revolution? [ R = (400 mm/2) = 200 mm ]

[pic]; v = 4.47 m/s

[pic]; f = 3.56 rev/s

*10-12. A 500-g damp shirt rotates against the wall of a washer at 300 rpm. The diameter of the rotating drum is 70 cm. What is the magnitude and direction of the resultant force on the shirt? [ R = (70 cm/2) = 35 cm; f = 300 rpm(60 s/min) = 1800 rev/s ]

[pic];

Fc = 2.24 x 107 N, toward the center

*10-13. A 70-kg runner rounds a track of radius 25 m at a speed of 8.8 m/s. What is the central force causing the runner to turn and what exerts the force?

[pic]; Fc = 217 N, friction

*10-14. In Olympic bobsled competition, a team takes a turn of radius 24 ft at a speed of 60 mi/h. What is the acceleration? How many g’s do passengers experience? (60 mi/h = 88 ft/s)

[pic]; ac = 323 ft/s2 or 10.1 g’s

Flat Curves and Banked Curves

10-15. On a rainy day the coefficient of static friction between tires and the roadway is only 0.4. What is the maximum speed at which a car can negotiate a turn of radius 80 m?

[pic];

vc = 17.7 m/s or 63.8 km/h

10-16. A bus negotiates a turn of radius 400 ft while traveling at a speed of 60 mi/h. If slipping just begins at this speed, what is the coefficient of static friction between the tires and the road? (60 mi/h = 88 ft/s)

[pic]; (s = 0.605

10-17. Find the coefficient of static friction necessary to sustain motion at 20 m/s around a turn of radius 84 m.

[pic]; (s = 0.486

*10-18. A 20-kg child sits 3 m from the center of a rotating platform. If (s = 0.4, what is the max

imum number of revolutions per minute that can be achieved without slipping?

(Slipping occurs when the centripetal force equals the maximum force of static friction.)

[pic];

f = 0.182 rev/s (60 s/min); f = 10.9 rpm

*10-19. A platform rotates freely at 100 rpm. If the coefficient of static friction is 0.5, how far from the center of the platform can a bolt be placed to without slipping?

f = 100 rev/min (1 min/60 s) = 1.67 rev/s; (s = 0.5; R = ?

[pic]; R = 21.1 cm

10-20. Find the required banking angle to negotiate the curve of Prob.10-15 without slipping.

[pic]; ( = 21.80

10-21. Find the required banking angle for Problem 10-16 to prevent slipping?

[pic]; ( = 31.20

10-22. The optimum banking angle for a curve of radius 20 m is found to be 280. For what speed was this angle designed?

[pic]; v = 10.3 m/s

*10-23. A curve in a road 9 m wide has a radius of 96 m. How much higher than the inside edge should the outside edge be ...



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