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Unformatted text preview: practice 05 ALIBHAI, ZAHID 1 Latest unpenalized work: Feb 18 2007 Sunday 04:00 (after this date you can not make a perfect score). Work cutoff: Feb 18 2007, 4:00 am. Question 1 part 1 of 1 10 points A copper block rests 46 . 9 cm from the cen ter of a steel turntable. The coefficient of static friction between block and surface is . 49. The turntable starts from rest and ro tates with a constant angular acceleration of . 616 rad / s 2 . The acceleration of gravity is 9 . 8 m / s 2 . After what interval will the block start to slip on the turntable? Answer in units of s. Question 2 part 1 of 2 10 points The coefficient of static friction between the person and the wall is 0 . 77 . The radius of the cylinder is 5 . 22 m . The acceleration of gravity is 9 . 8 m / s 2 . An amusement park ride consists of a large vertical cylinder that spins about its axis fast enough that any person inside is held up against the wall when the floor drops away. 5 . 22 m What is the minimum angular velocity min needed to keep the person from slip ping downward? Answer in units of rad / s. Question 3 part 2 of 2 10 points Suppose the person, whose mass is m , is being held up against the wall with an angular velocity of = 2 min . The magnitude of the frictional force be tween the person and the wall is 1. F = 1 2 mg . 2. F = 3 mg . 3. F = 2 mg . 4. F = mg . 5. F = 5 mg . 6. F = 1 5 mg . 7. F = 1 4 mg . 8. F = 4 mg . 9. F = 1 3 mg . Question 4 part 1 of 2 10 points An ant of mass m clings to the rim of a flywheel of radius r , as shown. The flywheel rotates clockwise on a horizontal shaft S with constant angular velocity . As the wheel rotates, the ant revolves past the stationary points I , II , III , and IV . The ant can adhere to the wheel with a force much greater than its own weight. r S I II III IV Ant It will be most difficult for the ant to adhere to the wheel as it revolves past which of the four points? practice 05 ALIBHAI, ZAHID 2 1. II 2. IV 3. It will be equally difficult for the ant to adhere to the wheel at all points. 4. III 5. I Question 5 part 2 of 2 10 points What is the magnitude of the minimum adhesion force necessary for the ant to stay on the flywheel at point III ? 1. F = m 2 r mg 2. F = m 2 r + mg 3. F = m 2 r 2 4. F = m 2 r 2 + mg 5. F = mg Question 6 part 1 of 1 10 points A highway curves to the left with radius of curvature R = 41 m. The highways surface is banked at = 29 so that the cars can take this curve at higher speeds. Consider a car of mass 892 kg whose tires have static friction coefficient = 0 . 61 against the pavement. The acceleration of gravity is 9 . 8 m / s 2 . top view R = 41 m 2 9 rear view = . 6 1 How fast can the car take this curve without skidding to the outside of the curve?...
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 Spring '08
 Turner
 Force, Friction, Mass, Work

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