Deck 6: Further Applications of Newtons Laws

Question 1

The word normal in the phrase normal force signifies that the force

A) has a standard magnitude.
B) is usually encountered.
C) is equal and opposite to the weight.
D) has a direction perpendicular to some designated plane.

Answer 1

has a direction perpendicular to some designated plane.

Question 2

For the case of a static frictional force on a body, all of the following are characteristic except

A) it requires another force on the same body directed other than along the axis of the static frictional force itself.
B) it is generated by the application of a force directed opposite to the direction of the frictional force itself.
C) it has a magnitude independent of the area of the surface in contact.
D) it requires motion of the body.

Answer 2

it requires motion of the body.

Question 3

For each of the following forces, the accompanying change produces a change in the direction (as measured in a rectangular coordinate system) of the force, except for the

A) restoring force of a stretched spring if the direction of the displacement from equilibrium changes.
B) kinetic frictional force, if the direction of the velocity changes.
C) centripetal force, as the object moves along its circular path.
D) gravitational force, as the object moves along its parabolic path.

Answer 3

gravitational force, as the object moves along its parabolic path.

Question 4

In physics, the phrase the acceleration due to gravity refers to

A) the (roughly constant) acceleration of a body that is falling near the surface of the Earth.
B) the ratio of the weight of a body near the surface of the Earth to the mass of the body.
C) both of the above.
D) none of the above.

Question 5

A block slides down a frictionless inclined plane. All of the following are correct except for

A) the velocity of the block changes with time.
B) the acceleration of the block is less than the acceleration of gravity.
C) the normal force on the block changes with time.
D) the normal force on the block is less than the weight of the block.

Question 6

A block slides down a frictionless inclined plane. The block is held in place on the plane until the platform on which the plane rests is given an acceleration to the right. The block is then released. During the time the platform is accelerated

A) the velocity of the block changes with time.
B) the block may accelerate up the incline.
C) the normal force on the block changes with time.
D) the normal force on the block is less than the weight of the block.

Question 7

A block slides down a frictionless inclined plane. All of the following are correct except

A) the velocity of the block changes with time.
B) the acceleration of the block is less than the acceleration of gravity.
C) the normal force on the block is less than the weight of the block.
D) the frictional force on the block is less than the weight of the block.

Question 8

A automobile moving at 90.0 km/hr travels around a level curve of radius 100.0 m. The minimum possible coefficient of friction required for the auto not to slip sideways is

A) 0.
B) 0.02.
C) 0.64.
D) 0.83.

Question 9

A small block slides down the surface of a large stationary sphere. All of the following are independent of the location of the block on the sphere except for

A) the radius of curvature of path.
B) the coefficient of friction between the block and the sphere.
C) the angle the surface of contact between the block and the sphere makes with a horizontal line.
D) Hold it! There are no exceptions.

Question 10

A small block slides down the surface of a large stationary sphere. All of the following depend on the location of the block on the sphere except for

A) the block's speed.
B) the block's velocity.
C) the acceleration of gravity.
D) Hold it! There are no exceptions.

Question 11

A small block slides down the surface of a large stationary sphere. The magnitude of all of the following depend on the location of the body on the sphere except for the

A) kinetic friction.
B) centripetal force.
C) normal force.
D) weight.

Question 12

In some amusement parks, one particular ride requires the occupant to stand on the floor, leaning against the (vertical) inside wall of a huge cylinder that rotates about its axis of symmetry. At some instant during the ride, the floor is "removed" so that it no longer makes contact with the feet of the occupant, who remains "pressed" against the wall. Parameters relevant to the safety of the ride include all of the following except

A) the coefficient of friction between the wall and the clothes of the occupant.
B) the radius of curvature of the cylinder.
C) the weight of the occupant.
D) the tangential speed of the cylinder.

Question 13

A smooth block rests on the surface of a horizontal plane. As one end of the plane is slowly raised, the magnitude of the normal force on the block

A) decreases.
B) remains unchanged.
C) increases.
D) is unknown; insufficient information is given to answer this question.

Question 14

A smooth block rests on the surface of a horizontal plane. As one end of the plane is slowly raised, the block starts sliding down. The magnitude of the frictional force on the block

A) decreases.
B) remains unchanged.
C) increases.
D) is unknown; insufficient information is given to answer this question.

Question 15

A smooth block rests on the surface of a horizontal plane. As one end of the plane is slowly raised, the block starts sliding down. The speed of the block

A) decreases with time.
B) remains unchanged.
C) increases with time.
D) is unknown; insufficient information is given to answer this question.

Question 16

Consider a crate of mass 5.0 kg resting on the floor. A man pushing along a line making an angle of 15° with the plane of the floor is barely able to overcome the friction (coefficient µ_k = 0.45) and slide the crate with constant speed. The minimum force necessary to produce this motion is

A) 0 N.
B) 23 N.
C) 46 N.
D) infinite.

Question 17

Consider a crate of mass 5.0 kg resting on the floor. A man pushing along a line making an angle of 15° with the plane of the floor is overcoming the frictional force (coefficient µ_k = 0.45) and sliding the crate with an acceleration of 1.0 m/s². The minimum force necessary to produce this motion is

A) 15 N.
B) 23 N.
C) 32 N.
D) Hold it! Insufficient information is given for an unambiguous response.

Question 18

A block is at rest on a frictionless incline that makes an angle, $\theta$ , with the horizontal. The normal force on the block is proportional to

A) sin $\theta$ .
B) cos $\theta$
C) tan $\theta$
D) Hold it! This force is independent of $\theta$

Question 19

A block is at rest on frictionless incline that makes an angle, $\theta$ , with the horizontal. The frictional force on the block is proportional to

A) sin $\theta$
B) cos $\theta$
C) tan $\theta$
D) Hold it! This force is independent of $\theta$

Question 20

A block is at rest on a frictionless horizontal plane. As one end of the plane is slowly raised, the block eventually "breaks loose" when the plane makes an angle, $\theta$ , with the horizontal. At this moment the coefficient of static friction is

A) sin $\theta$
B) cos $\theta$
C) tan $\theta$
D) cot $\theta$

Question 21

A block is at rest on a frictionless horizontal plane. As one end of the plane is slowly raised, the block eventually "breaks loose" when the plane makes an angle $\theta$ , with the horizontal. The coefficient of kinetic friction can be calculated by assuming

A) constant displacement of the block.
B) constant speed of the block.
C) constant acceleration of the block.
D) none of the above.

Question 22

A mass of 2.0 kg in contact with a frictionless horizontal plane is moving horizontally due to an external horizontal force of 6.0 N. Assuming that the acceleration of gravity is 10 m/s², the magnitude of the mass's acceleration is

A) 0.50 m/s².
B) 1.0 m/s².
C) 2.0 m/s².
D) 3.0 m/s².

Question 23

A mass of 2.0 kg in contact with a horizontal plane (coefficient of friction 0.25) is moving horizontally due to an external horizontal force of 6.0 N. Assuming that the acceleration of gravity is 10 m/s², the magnitude of the mass's acceleration is

A) 0.50 m/s².
B) 1.0 m/s².
C) 2.0 m/s².
D) 3.0 m/s².

Question 24

A 1.0-kg mass hangs at the end of a strong, massless cord attached to a 2.0-kg mass. The 2.0-kg mass hangs at the end of another strong, massless cord. A force applied to the "upper" cord accelerates the system upward at 10 m/s². Assuming that the acceleration of gravity is 10 m/s², the tension in the upper cord is

A) 20 N.
B) 30 N.
C) 40 N.
D) 60 N.

Question 25

A 1.0 kg mass hangs at the end of a strong, massless cord attached to a 2.0-kg mass. The 2.0-kg mass hangs at the end of another strong, massless cord. A force applied to the "upper" cord accelerates the system upward at 10 m/s². Assuming that the acceleration of gravity is 10 m/s², the tension in the lower cord is

A) 20 N.
B) 30 N.
C) 40 N.
D) 60 N.

Question 26

A 1.0-kg mass rests on an inclined plane (angle of incline = 60°). Assuming that the acceleration of gravity is 10 m/s², the normal force acting on the mass is

A) 8.5 N.
B) 5.0 N.
C) 10 N.
D) 0.0 N.

Question 27

If the velocity of an object undergoing uniform circular motion is doubled, the centripetal force will

A) remain the same.
B) increase by a factor of 2.
C) increase by a factor of 4.
D) decrease by a factor of 2.

Question 28

If the radius of an object undergoing uniform circular motion is doubled, the centripetal force will

A) remain the same.
B) increase by a factor of 2.
C) increase by a factor of 4.
D) decrease by a factor of 2.

Question 29

A spring with a force constant of 5.0 N/m is used to suspend a 2.0-N weight. The displacement of the mass is

A) 0.40 m.
B) 10 m.
C) 2.5 m.
D) -2.5 m.

Question 30

Two springs with force constants of 50 N/m and 100 N/m are connected in series. A 1.0-kg mass is suspended from the springs. Assuming that the acceleration of gravity is 10 m/s², the total amount of stretch is

A) 13 cm.
B) 30 cm.
C) 40 cm.
D) 50 cm.

Question 31

Two springs with force constants of 30 N/m and 20 N/m are connected in parallel. When an object is hung from the springs, they extend 0.30 m. Assuming that the acceleration of gravity is 10 m/s², the mass of the object is

A) 0.50 kg.
B) 1.0 kg.
C) 1.5 kg.
D) 2.0 kg.

Question 32

A mass of 4.5 kg causes a 15-cm extension of a spring. Assuming that the acceleration of gravity is 10 m/s², the force constant of the spring is

A) 3.0 N/m.
B) 7.0 N/m.
C) 30 N/m.
D) 3.0 $\times$ 10² N/m.

Question 33

Consider two masses: M₁= 2.0 kg and M₂ =1.5 kg. Mass M₁ moves on a horizontal surface where the coefficient of kinetic friction m_k = 0.40. Mass M₂ is hanging freely. The two masses are connected by a strong cord of negligible mass that extends over a frictionless pulley. Assuming that the acceleration of gravity is 10 m/s², the acceleration of M₂ is

A) 0 m/s².
B) 2.0 m/s².
C) 10 m/s².
D) 5.0 m/s².

Question 34

Consider two masses: M₁ = 2.0 kg and M₂ = 1.5 kg. Mass M₁ moves on a horizontal surface where the coefficient of kinetic friction m_k = 0.40. Mass M₂ is hanging freely. The two masses are connected by a strong cord of negligible mass that extends over a frictionless pulley. Assuming that the acceleration of gravity is 10 m/s², the tension in the cord is

A) 0 N.
B) 12 N.
C) 15 N.
D) 20 N.

Question 35

Consider two masses: M₁ = 1.4 kg and M₂ = 2.5 kg connected by a strong cord of negligible mass that extends over a frictionless pulley. The masses are placed on surfaces that make angles of 27° and 60° respectively with respect to the horizontal. The coefficient of kinetic friction between the surfaces and the masses is 0.30. Assuming that the acceleration of gravity is 10 m/s², the acceleration of M₁
Is

A) 0 m/s².
B) 1.0 m/s².
C) 2.0 m/s².
D) 3.0 m/s².

Question 36

A 50.0-N horizontal force is applied to a 40.0-N crate that is placed on a 15° ramp. The coefficient of kinetic friction between the crate and the ramp is 0.25. The net force acting on the crate is

A) 25 N.
B) 30 N.
C) 40 N.
D) 50 N.

Question 37

A variable horizontal force, F, is applied to a 5.0-kg object placed on a flat horizontal plane. The coefficient of static friction between the object and the surface is 0.30. Assuming that the acceleration of gravity is 10 m/s², the range of force that can be applied to the object without initiating any motion is

A) 0 < F.
B) 0 < F < 10 N.
C) 0 < F < 15 N.
D) 0 < F < 35 N.

Question 38

An object slides down a rough surface that is inclined by 30° with a constant acceleration of 2.0 m/s². The coefficient of kinetic friction between the object and the surface is

A) 0.25.
B) 0.35.
C) 0.45.
D) 0.55.

Question 39

An object is placed on a board. The coefficient of static friction between the object and the board is 0.40. One end of the board is slowly raised until the object begins to slide. The angle that the board makes when the object begins to slide is

A) 16°.
B) 22°.
C) 74°.
D) unknown; the answer cannot be determined without knowing the mass of the object.

Question 40

A 10.0-kg cannonball is dropped from a tall bridge into a river. The diameter of the cannonball is 20.0 cm, and the aerodynamic constant for the ball is C = 0.100. Assuming that the acceleration of gravity is 10.0 m/s² and that the density of air is 1.30 kg/m³, the terminal velocity of the cannonball is

A) 110 m/s.
B) 165 m/s.
C) 221 m/s.
D) 275 m/s.

Question 41

Consider two masses, M₁ = 3.0 kg and M₂ = 2.5 kg, connected by a strong cord of negligible mass that extends over a frictionless pulley. Mass M₁ is placed on a surface that makes an angle of 30° with respect to the horizontal, while mass M₂ is hanging freely. The coefficient of kinetic friction between the surface and the mass is 0.25. Assuming that the acceleration of gravity is 10 m/s², the acceleration of mass M₁ is

A) 0 m/s².
B) 1.0 m/s².
C) 2.0 m/s².
D) 3.4 m/s².

Question 42

A car traveling at 90 km/h is moving around a curve that has a radius of 450 m. Assuming that the acceleration of gravity is 10 m/s², the angle at which the road should be banked if the driver wishes not to rely on lateral friction is

A) 0.50°.
B) 7.9°.
C) 14°.
D) unknown; the answer cannot be determined without knowing the mass of the object.

Question 43

For this problem, assume that the acceleration due to gravity, g, is 10 m/s². A Mazda Miata is traveling at 90.0 km/h around a curve whose radius is 475 m. The mass of the Miata plus driver and passenger is 1350 kg. Assuming that the acceleration of gravity is 10.0 m/s², the centripetal force required to maintain the car around the curve is

A) 1.49 $\times$ 10³ N.
B) 1.78 $\times$ 10³ N.
C) 1.81 $\times$ 10³ N.
D) 1.86 $\times$ 10³ N.

Question 44

A 30-N horizontal force is applied to a 1.5-kg object lying on a ramp that makes a 30° angle with the horizontal. The normal force acting on the object is

A) 13 N.
B) 15 N.
C) 28 N.
D) 45 N.

Question 45

An object receives an initial push, giving it an initial velocity of 2.0 m/s. It then slides across a rough surface and comes to a stop after traveling a distance of 0.5 m. Assuming that the acceleration of gravity is 10 m/s², the coefficient of kinetic friction between the object and the surface is

A) 0.2.
B) 0.4.
C) 0.6.
D) unknown; the answer cannot be determined without knowing the mass of the object.

Question 46

A package is placed on the back of a flatbed truck. The coefficient of static friction between the package and the bed of the truck is f_s < 0.40. Assuming that the acceleration of gravity is 10 m/s², the maximum velocity tat which he truck can travel around a 25-m-radius curve without losing the load is

A) 36 km/h.
B) 10 km/h.
C) 1.0 * 10² km/h.
D) unknown; the answer cannot be determined without knowing the mass of the object.

Question 47

A strong light rope connects two objects of masses M₁ and M₂. A force applied to M₂ is accelerating the system. When the coefficient of friction between the two objects and the surface doubles, the tension in the rope connecting the two objects

A) remains the same.
B) doubles.
C) increases by a factor of $\sqrt { 2 }$
D) cannot be determined without further information.

Question 48

A 10.0-m rope is placed on a rooftop that is pitched at 20°. The coefficient of static friction between the rope and the roof is 0.60. The longest length of rope that can safely hang over the edge of the roof without pulling the remaining rope off

A) is 1.0 m.
B) is 1.7 m.
C) is 2.5 m.
D) cannot be determined unless we know the total mass of the rope.

Question 49

A 5.0-kg box slides up an inclined plane at a constant speed when a 25-N force is applied to it parallel to the plane of incline. Assuming that the acceleration of gravity is 10 m/s², the coefficient of kinetic friction between the box and the incline is

A) f_k = 0.20.
B) f_k = 0.25.
C) f_k = 0.30.
D) f_k = 0.35.

Question 50

A roller coaster traveling at 15 m/s goes through a dip in the track whose radius of curvature is 45 m. Assuming that the acceleration of gravity is 10 m/s², the number of "g's" the riders experience is

A) 1.5 g.
B) 0.50 g.
C) 5.0 g.
D) 6.0 g.