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Exam 6: Applications of Newtons Laws

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Question 21

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A mass of 3.0 kg rests on a smooth surface inclined 34° above the horizontal. It is kept from sliding down the plane by a spring attached to a wall. The spring is aligned with the plane and has a spring constant of 120 N/m. How much does the spring stretch?

A) 360 cm
B) 240 cm
C) 14 cm
D) 24 cm
E) 36 cm

F) A) and B)
G) B) and D)

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Question 22

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A 1000-kg car is picking up speed as it goes around a horizontal curve whose radius is 100 m. The coefficient of static friction between the tires and the road is 0.350. At what speed will the car begin to skid sideways?

A) 9.25 m/s
B) 23.6 m/s
C) 34.3 m/s
D) 35.0 m/s
E) 18.5 m/s

F) B) and E)
G) D) and E)

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Question 23

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The force of static friction between two surfaces is independent of the area of contact between the surfaces.

A baseball player is running to second base at 5.03 m/s. When he is 4.80 m from the plate he goes into a slide. The coefficient of kinetic friction between the player and the ground is 0.180. What is his speed when he reaches the plate?

A policeman investigating an accident measures the skid marks left by a car. He determines that the distance between the point that the driver slammed on the brakes and the point where the car came to a stop was 28.0 m. From a reference manual he determines that the coefficient of kinetic friction between the tires and the road under the prevailing conditions was 0.300. How fast was the car going when the driver applied the brakes? (This car was not equipped with anti-lock brakes.)

An airplane is flying with constant speed of 300 m/s along a horizontal circle with a radius of 15,000 m. If the lift force of the air on the wings is perpendicular to the wings, at what angle relative to the horizontal should the wings be banked?

A 60.0-kg mass person wishes to push a 120-kg mass box across a level floor. The coefficient of static friction between the person's shoes and the floor is 0.700. What is the maximum coefficient of static friction between the box and the floor such that the person can push horizontally on the box and cause it to start moving?

Why does a cyclist tilt her bicycle on a curve?

FIGURE 6-7 -A 30.0-kg load is being lifted with constant speed using the ideal pulley arrangement shown in Figure 6-7. What is the magnitude of the force F?

The force of kinetic friction between two surfaces is dependent on the relative speed of the two surfaces.

In a carnival ride, passengers stand with their backs against the wall of a cylinder. The cylinder is set into rotation and the floor is lowered away from the passengers, but they remain stuck against the wall of the cylinder. For a cylinder with a 2.0-m radius, what is the minimum speed that the passengers can have for this to happen if the coefficient of static friction between the passengers and the wall is 0.25?

If a car slows down with the wheels rolling, is the frictional force between the tires and the ground kinetic or static?

A tightrope walker with a mass of 60.0 kg stands at the center of a rope which was initially strung horizontally between two poles. His weight causes the rope to sag symmetrically, making an angle of 4.80° with the horizontal. What is the tension in the rope?

Diff: 1 Var: 5 Page Ref: Sec. 6-2 -A mass of 40.0 grams is attached to a vertical spring with a spring constant k = 20.0 N/m and lowered slowly until the spring stops stretching. How much does the spring stretch?

A 3.00-kg mass and a 5.00-kg mass hang vertically at the ends of a rope that goes over an ideal pulley. If the masses are released, what is the resulting acceleration of the masses?

FIGURE 6-14 -A 20.0-gram mass is attached to a 120 cm-long string as shown in Figure 6-14. The tension in the string is measured to be 0.200 N. What is the angle α?

Pulling out of a dive, the pilot of an airplane guides his plane into a vertical circle with a radius of 600 m. At the bottom of the dive, the speed of the airplane is 150 m/s. What is the apparent weight of the 70.0-kg pilot at that point?

When an object experiences uniform circular motion, the direction of the acceleration is

A 2-kg ball is moving with a constant speed of 5 m/s in a horizontal circle whose radius is 50 cm. What is the magnitude of the net force on the ball?

A 600-kg car is going over a curve with a radius of 120 m that is banked at an angle of 25° with a speed of 30.0 m/s. The coefficient of static friction between the car and the road is 0.30. What is the normal force exerted by the road on the car?