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Exam 5: Using Newtons Laws: Friction, Circular Motion, Drag Forces

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Question 21

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FIGURE 5-1 -In Fig. 5-1, the block of mass m is at rest on an inclined plane that makes an angle θ with the horizontal. The force of static friction f must be such that

A) f > mg.
B) f > mg cosθ.
C) f > mg sinθ.
D) f = mg cosθ.
E) f = mg sinθ.

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Question 22

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FIGURE 5-5 -A 4.00-kg block rests on a 30.0 degree incline as shown in Fig. 5-5. If the coefficient of static friction between the block and the incline is 0.700, with what magnitude force must a horizontal force act on the block to start it moving up the incline?

A) 34.0 N
B) 51.1 N
C) 54.7 N
D) 84.1 N
E) 76.4 N

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Question 23

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The magnitude of the drag force on a 20.0-kg object is proportional to its speed. The object has a terminal velocity 80 m/s. What is the magnitude of the drag force on the object when it is falling with a speed 30 m/s?

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?

What is the terminal velocity of a 6.00-kg mass object in falling with a drag force with a magnitude that depends on speed, v, as F_drag = (30.0 N∙s/m) v?

FIGURE 5-5 -A 4.00-kg block is sliding up the plane on a 30.0 degree incline as shown in Fig. 5-5. If the coefficient of kinetic friction between the block and the incline is 0.700, what will be the acceleration of the block if a 50.0-N horizontal force pushes on the block?

A child stands on a playground merry-go-round a distance of 1.50 m from the rotation axis. The coefficient of static friction between the child's shoes and the surface of the merry-go-round is 0.700. Assuming the acceleration of gravity is 9.81 m/s², what is the maximum constant angular speed of the merry-go-round for which the child will not start to slide?

A 55.0-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.300. What horizontal force must be applied to the box for it to start sliding along the surface?

For uniform circular motion, the velocity and acceleration vectors are perpendicular to each other at every point in the path.

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?

As a car drives with its tires rolling freely without any slippage, the type of friction acting between the tires and the road is

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

FIGURE 5-2 -Fig. 5-2 indicates the current position of an object traveling at constant speed clockwise around the circle. Which arrow best represent the direction of the current acceleration of the object?

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

A car of mass m goes around a banked curve of radius r with speed v. If the road is frictionless due to ice, the car can still negotiate the curve if the horizontal component of the normal force on the car from the road is equal in magnitude to

Is it possible for an object moving around a circular path to have both centripetal and tangential acceleration?

An airplane is flying with constant speed along a horizontal circle. Is the direction of its acceleration constant?

A 1.20-kg ball is hanging on the end of a rope. The rope makes an angle 25.0° from the vertical when a 15.0 m/s horizontal wind blows. If the wind's force on the rope is negligible, what is the drag force on the ball?

A packing crate slides down an inclined ramp at constant velocity. Thus we can deduce that

A ball is tied to the end of a cable of negligible mass. The ball is spun in a circle with a radius 2.00 m making 0.700 revolutions per second. What is the centripetal acceleration of the ball?