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100問 • 2年前

問題一覧

A jet plane in straight horizontal flight passes over your head. When it is directly above you, the sound seems to come from a point behind the plane in a direction 30◦ from the vertical. The speed of the plane is:

half the speed of sound

Two bodies are falling with negligible air resistance, side by side, above a horizontal plane. If one of the bodies is given an additional horizontal acceleration during its descent, it:

strikes the plane at the same time as the other body

Of the following situations, which one is impossible?

A body having constant velocity and variable acceleration

Throughout a time interval, while the speed of a particle increases as it moves along the x axis, its velocity and acceleration might be:

negative and negative, respectively

A particle moves on the x axis. When its acceleration is positive and increasing:

none of the above must be true

A ball is in free fall. Its acceleration is:

downward during both ascent and descent

A ball is in free fall. Upward is taken to be the positive direction. The displacement of the ball during a short time interval is:

positive during ascent and negative during descent

Which one of the following statements is correct for an object released from rest?

The average velocity during the first second of time is 4.9 m/s

A freely falling body has a constant acceleration of 9.8 m/s2. This means that:

the speed of the body increases by 9.8 m/s during each second

An object is shot vertically upward. While it is rising:

its velocity is upward and its acceleration is downward

A feather, initially at rest, is released in a vacuum 12 m above the surface of the earth. Which of the following statements is correct?

The acceleration of the feather remains constant during the fall

The area under a velocity-time graph represents:

displacement

Displacement can be obtained from:

the area under a velocity-time graph

An object has a constant acceleration of 3 m/s2. The coordinate versus time graph for this object has a slope:

that increases with time

The coordinate-time graph of an object is a straight line with a positive slope. The object has:

constant velocity

We say that the displacement of a particle is a vector quantity. Our best justification for this assertion is:

operating with displacements according to the rules for manipulating vectors leads to results in agreement with experiments

If the magnitude of the sum of two vectors is less than the magnitude of either vector, then:

the scalar product of the vectors must be negative

If the magnitude of the sum of two vectors is greater than the magnitude of either vector, then:

none of the above

Velocity is defined as:

rate of change of position with time

Acceleration is defined as:

rate of change of velocity with time

Which of the following is a scalar quantity?

Speed

Which of the following is a vector quantity?

None of these

Which of the following is NOT an example of accelerated motion?

Horizontal component of projectile motion

Two bodies are falling with negligible air resistance, side by side, above a horizontal plane. If one of the bodies is given an additional horizontal acceleration during its descent, it:

strikes the plane at the same time as the other body

The velocity of a projectile equals its initial velocity added to:

a constantly increasing downward velocity

A stone thrown from the top of a tall building follows a path that is:

parabolic

Identical guns fire identical bullets horizontally at the same speed from the same height above level planes, one on the Earth and one on the Moon. Which of the following three statements is/are true? I. The horizontal distance traveled by the bullet is greater for the Moon. II. The flight time is less for the bullet on the Earth. III. The velocity of the bullets at impact are the same.

I and II only

A bullet shot horizontally from a gun:

strikes the ground at approximately the same time as one dropped vertically from the same point at the same instant

A bomber flying in level flight with constant velocity releases a bomb before it is over the target. Neglecting air resistance, which one of the following is NOT true?

The horizontal velocity of the plane equals the vertical velocity of the bomb when it hits the target

An object is shot from the back of a railroad flatcar moving at 40 km/h on a straight horizontal road. The launcher is aimed upward, perpendicular to the bed of the flatcar. The object falls:

on the flatcar

A particle moves at constant speed in a circular path. The instantaneous velocity and instan- taneous acceleration vectors are:

perpendicular to each other

A stone is tied to a string and whirled at constant speed in a horizontal circle. The speed is then doubled without changing the length of the string. Afterward the magnitude of the acceleration of the stone is:

half as great

Two objects are traveling around different circular orbits with constant speed. They both have the same acceleration but object A is traveling twice as fast as object B. The orbit radius for object A is

four times

An example of an inertial reference frame is:

a reference frame attached to the center of the universe

An object moving at constant velocity in an inertial frame must:

have zero net force on it

SI units a force is numerically equal to the ______ when the force is applied to it.

acceleration of the standard kilogram

Which of the following quantities is NOT a vector?

Mass

A newton is the force:

that gives a 1 kg body an acceleration of 1 m/s2

The unit of force called the newton is:

1kg·m/s2

A force of 1N is:

1kg·m/s2

Acceleration is always in the direction:

of the net force

The term “mass” refers to the same physical concept as:

inertia

The inertia of a body tends to cause the body to:

resist any change in its motion

Mass differs from weight in that:

weight is a force and mass is not

The mass of a body:

is independent of the free-fall acceleration

The mass and weight of a body:

have the same ratio as that of any other body placed at that location

Two objects, one having three times the mass of the other, are dropped from the same height in a vacuum. At the end of their fall, their velocities are equal because:

none of the above

A feather and a lead ball are dropped from rest in vacuum on the Moon. The acceleration of the feather is:

the same as that of the lead ball

Equal forces F act on isolated bodies A and B. The mass of B is three times that of A. The magnitude of the acceleration of A is:

three times that of B

A car travels east at constant velocity. The net force on the car is:

zero

An applied. This force produces an acceleration: object rests on a horizontal frictionless surface. A horizontal force of magnitude F is

always

A heavy steel ball B is suspended by a cord from a block of wood W. The entire system is dropped through the air. Neglecting air resistance, the tension in the cord is:

zero

You stand on a spring scale on the floor of an elevator. Of the following, the scale shows the highest reading when the elevator:

moves upward with increasing speed

You stand on a spring scale on the floor of an elevator. Of the following, the scale shows the highest reading when the elevator:

moves downward with decreasing speed

The “reaction” force does not cancel the “action” force because:

they are on different bodies

A book rests on a table, exerting a downward force on the table. The reaction to this force is:

the force of the table on the book

A lead block is suspended from your hand by a string. The reaction to the force of gravity on the block is the force exerted by:

the block on Earth

A brick slides on a horizontal surface. Which of the following will increase the magnitude of the frictional force on it?

Putting a second brick on top

The coefficient of kinetic friction:

is none of the above

When the brakes of an automobile are applied, the road exerts the greatest retarding force:

just before the wheels start to slide

A force F (larger than the largest possible force of static friction) is applied to the left to an object moving to the right on a horizontal surface. Then:

the object must be slowing down

A professor holds an eraser against a vertical chalkboard by pushing horizontally on it. He pushes with a force that is much greater than is required to hold the eraser. The force of friction exerted by the board on the eraser increases if he:

pushes so his force is slightly downward but has the same magnitude

Why do raindrops fall with constant speed during the later stages of their descent?

Air resistance just balances the force of gravity

A ball is thrown downward from the edge of a cliff with an initial speed that is three times the terminal speed. Initially its acceleration is

upward and greater than g

A ball is thrown upward into the air with a speed that is greater than terminal speed. On the way up it slows down and, after its speed equals the terminal speed but before it gets to the top of its trajectory:

it continues to slow down

A ball is thrown upward into the air with a speed that is greater than terminal speed. It lands at the place where it was thrown. During its flight the force of air resistance is the greatest:

just after it is thrown

Uniform circular motion is the direct consequence of:

a force of constant magnitude that is always directed toward the same fixed point

An object moving in a circle at constant speed:

has an acceleration of constant magnitude

An object moves around a circle. If the radius is doubled keeping the speed the same then the magnitude of the centripetal force must be:

half as great

An object moves in a circle. If the mass is tripled, the speed halved, and the radius unchanged, then the magnitude of the centripetal force must be multiplied by a factor of:

3/4

If a satellite moves above Earth’s atmosphere in a circular orbit with constant speed, then:

its acceleration is toward the Earth

The driver of a 1000-kg car tries to turn through a circle of radius 100 m on an unbanked curve at a speed of 10m/s. The actual frictional force between the tires and slippery road has a magnitude of 900 N. The car:

slides off to the outside of the curve

A coin is placed on a horizontal phonograph turntable. Let N be the magnitude of the normal force exerted by the turntable on the coin, f be the magnitude of the frictional force exerted by the turntable on the coin, and fs, max be the maximum possible force of static friction. The speed of the turntable is increased in small steps. If the coin does not slide, then

f increases and both N and fs, max stay the same

Which of the following is NOT a correct unit for work?

watt

Which of the following groups does NOT contain a scalar quantity?

displacement, acceleration, force

An object moves in a circle at constant speed. The work done by the centripetal force is zero because:

the centripetal force is perpendicular to the velocity

The work done by gravity during the descent of a projectile:

is positive

A baseball is hit high into the upper bleachers of left field. Over its entire flight the work done by gravity and the work done by air resistance, respectively, are:

negative; negative

A line drive to the shortstop is caught at the same height as it was originally hit. Over its entire flight the work done by gravity and the work done by air resistance, respectively, are:

zero; negative

The mechanical advantage of any machine is:

the ratio of the force exerted by the machine to the force applied to it

In the object vertically, there is a reduction in: raising an object to a given height by means of an inclined plane, as compared with raising

force required

A watt is:

kg · m2 /s3

Power has the dimensions of:

ML2 /T3

Which of the following five units represents a quantity that is NOT the same as the other four?

watt

A watt·second is a unit of:

energy

A watt per hour is a unit of:

none of these

A kilowatt·hour is a unit of:

work

Only if a force on a particle is conservative:

is its work zero when the particle moves exactly once around any closed path

A nonconservative force:

none of the above

The sum of the kinetic and potential energies of a system of objects is conserved:

none of the above

A force on a particle is conservative if:

its work depends on the end points of every motion, not on the path between

Two objects interact with each other and with no other objects. Initially object A has a speed of 5 m/s and object B has a speed of 10 m/s. In the course of their motion they return to their initial positions. Then A has a speed of 4 m/s and B has a speed of 7 m/s. We can conclude:

mechanical energy was decreased by nonconservative forces

A good example of kinetic energy is provided by:

a tornado

No kinetic energy is possessed by:

an elevator standing at the fifth floor

The wound spring of a clock possesses:

potential but no kinetic energy

A body at rest in a system is capable of doing work if:

it is free to move in such a way as to decrease the potential energy of the system

Which one of the following five quantities CANNOT be used as a unit of potential energy?

gram·cm/s2

Suppose that the fundamental dimensions are taken to be: force (F), velocity (V) and time (T). The dimensions of potential energy are then:

FVT

A golf ball is struck by a golf club and falls on a green three meters above the tee. The potential energy of the Earth-ball system is greatest:

when the ball reaches the highest point in its flight

100

An elevator is rising at constant speed. Consider the following statements: I. the upward cable force is constant II. the kinetic energy of the elevator is constant III. the gravitational potential energy of the Earth-elevator system is constant IV. the acceleration of the elevator is zero V. the mechanical energy of the Earth-elevator system is constant:

only I, II, and IV are true

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問題一覧

half the speed of sound

Two bodies are falling with negligible air resistance, side by side, above a horizontal plane. If one of the bodies is given an additional horizontal acceleration during its descent, it:

strikes the plane at the same time as the other body

Of the following situations, which one is impossible?

A body having constant velocity and variable acceleration

Throughout a time interval, while the speed of a particle increases as it moves along the x axis, its velocity and acceleration might be:

negative and negative, respectively

A particle moves on the x axis. When its acceleration is positive and increasing:

none of the above must be true

A ball is in free fall. Its acceleration is:

downward during both ascent and descent

A ball is in free fall. Upward is taken to be the positive direction. The displacement of the ball during a short time interval is:

positive during ascent and negative during descent

Which one of the following statements is correct for an object released from rest?

The average velocity during the first second of time is 4.9 m/s

A freely falling body has a constant acceleration of 9.8 m/s2. This means that:

the speed of the body increases by 9.8 m/s during each second

An object is shot vertically upward. While it is rising:

its velocity is upward and its acceleration is downward

A feather, initially at rest, is released in a vacuum 12 m above the surface of the earth. Which of the following statements is correct?

The acceleration of the feather remains constant during the fall

The area under a velocity-time graph represents:

displacement

Displacement can be obtained from:

the area under a velocity-time graph

An object has a constant acceleration of 3 m/s2. The coordinate versus time graph for this object has a slope:

that increases with time

The coordinate-time graph of an object is a straight line with a positive slope. The object has:

constant velocity

We say that the displacement of a particle is a vector quantity. Our best justification for this assertion is:

operating with displacements according to the rules for manipulating vectors leads to results in agreement with experiments

If the magnitude of the sum of two vectors is less than the magnitude of either vector, then:

the scalar product of the vectors must be negative

If the magnitude of the sum of two vectors is greater than the magnitude of either vector, then:

none of the above

Velocity is defined as:

rate of change of position with time

Acceleration is defined as:

rate of change of velocity with time

Which of the following is a scalar quantity?

Speed

Which of the following is a vector quantity?

None of these

Which of the following is NOT an example of accelerated motion?

Horizontal component of projectile motion

Two bodies are falling with negligible air resistance, side by side, above a horizontal plane. If one of the bodies is given an additional horizontal acceleration during its descent, it:

strikes the plane at the same time as the other body

The velocity of a projectile equals its initial velocity added to:

a constantly increasing downward velocity

A stone thrown from the top of a tall building follows a path that is:

parabolic

I and II only

A bullet shot horizontally from a gun:

strikes the ground at approximately the same time as one dropped vertically from the same point at the same instant

A bomber flying in level flight with constant velocity releases a bomb before it is over the target. Neglecting air resistance, which one of the following is NOT true?

The horizontal velocity of the plane equals the vertical velocity of the bomb when it hits the target

An object is shot from the back of a railroad flatcar moving at 40 km/h on a straight horizontal road. The launcher is aimed upward, perpendicular to the bed of the flatcar. The object falls:

on the flatcar

A particle moves at constant speed in a circular path. The instantaneous velocity and instan- taneous acceleration vectors are:

perpendicular to each other

half as great

four times

An example of an inertial reference frame is:

a reference frame attached to the center of the universe

An object moving at constant velocity in an inertial frame must:

have zero net force on it

SI units a force is numerically equal to the ______ when the force is applied to it.

acceleration of the standard kilogram

Which of the following quantities is NOT a vector?

Mass

A newton is the force:

that gives a 1 kg body an acceleration of 1 m/s2

The unit of force called the newton is:

1kg·m/s2

A force of 1N is:

1kg·m/s2

Acceleration is always in the direction:

of the net force

The term “mass” refers to the same physical concept as:

inertia

The inertia of a body tends to cause the body to:

resist any change in its motion

Mass differs from weight in that:

weight is a force and mass is not

The mass of a body:

is independent of the free-fall acceleration

The mass and weight of a body:

have the same ratio as that of any other body placed at that location

Two objects, one having three times the mass of the other, are dropped from the same height in a vacuum. At the end of their fall, their velocities are equal because:

none of the above

A feather and a lead ball are dropped from rest in vacuum on the Moon. The acceleration of the feather is:

the same as that of the lead ball

Equal forces F act on isolated bodies A and B. The mass of B is three times that of A. The magnitude of the acceleration of A is:

three times that of B

A car travels east at constant velocity. The net force on the car is:

zero

An applied. This force produces an acceleration: object rests on a horizontal frictionless surface. A horizontal force of magnitude F is

always

A heavy steel ball B is suspended by a cord from a block of wood W. The entire system is dropped through the air. Neglecting air resistance, the tension in the cord is:

zero

You stand on a spring scale on the floor of an elevator. Of the following, the scale shows the highest reading when the elevator:

moves upward with increasing speed

You stand on a spring scale on the floor of an elevator. Of the following, the scale shows the highest reading when the elevator:

moves downward with decreasing speed

The “reaction” force does not cancel the “action” force because:

they are on different bodies

A book rests on a table, exerting a downward force on the table. The reaction to this force is:

the force of the table on the book

A lead block is suspended from your hand by a string. The reaction to the force of gravity on the block is the force exerted by:

the block on Earth

A brick slides on a horizontal surface. Which of the following will increase the magnitude of the frictional force on it?

Putting a second brick on top

The coefficient of kinetic friction:

is none of the above

When the brakes of an automobile are applied, the road exerts the greatest retarding force:

just before the wheels start to slide

A force F (larger than the largest possible force of static friction) is applied to the left to an object moving to the right on a horizontal surface. Then:

the object must be slowing down

pushes so his force is slightly downward but has the same magnitude

Why do raindrops fall with constant speed during the later stages of their descent?

Air resistance just balances the force of gravity

A ball is thrown downward from the edge of a cliff with an initial speed that is three times the terminal speed. Initially its acceleration is

upward and greater than g

it continues to slow down

A ball is thrown upward into the air with a speed that is greater than terminal speed. It lands at the place where it was thrown. During its flight the force of air resistance is the greatest:

just after it is thrown

Uniform circular motion is the direct consequence of:

a force of constant magnitude that is always directed toward the same fixed point

An object moving in a circle at constant speed:

has an acceleration of constant magnitude

An object moves around a circle. If the radius is doubled keeping the speed the same then the magnitude of the centripetal force must be:

half as great

An object moves in a circle. If the mass is tripled, the speed halved, and the radius unchanged, then the magnitude of the centripetal force must be multiplied by a factor of:

3/4

If a satellite moves above Earth’s atmosphere in a circular orbit with constant speed, then:

its acceleration is toward the Earth

slides off to the outside of the curve

f increases and both N and fs, max stay the same

Which of the following is NOT a correct unit for work?

watt

Which of the following groups does NOT contain a scalar quantity?

displacement, acceleration, force

An object moves in a circle at constant speed. The work done by the centripetal force is zero because:

the centripetal force is perpendicular to the velocity

The work done by gravity during the descent of a projectile:

is positive

A baseball is hit high into the upper bleachers of left field. Over its entire flight the work done by gravity and the work done by air resistance, respectively, are:

negative; negative

A line drive to the shortstop is caught at the same height as it was originally hit. Over its entire flight the work done by gravity and the work done by air resistance, respectively, are:

zero; negative

The mechanical advantage of any machine is:

the ratio of the force exerted by the machine to the force applied to it

In the object vertically, there is a reduction in: raising an object to a given height by means of an inclined plane, as compared with raising

force required

A watt is:

kg · m2 /s3

Power has the dimensions of:

ML2 /T3

Which of the following five units represents a quantity that is NOT the same as the other four?

watt

A watt·second is a unit of:

energy

A watt per hour is a unit of:

none of these

A kilowatt·hour is a unit of:

work

Only if a force on a particle is conservative:

is its work zero when the particle moves exactly once around any closed path

A nonconservative force:

none of the above

The sum of the kinetic and potential energies of a system of objects is conserved:

none of the above

A force on a particle is conservative if:

its work depends on the end points of every motion, not on the path between

mechanical energy was decreased by nonconservative forces

A good example of kinetic energy is provided by:

a tornado

No kinetic energy is possessed by:

an elevator standing at the fifth floor

The wound spring of a clock possesses:

potential but no kinetic energy

A body at rest in a system is capable of doing work if:

it is free to move in such a way as to decrease the potential energy of the system

Which one of the following five quantities CANNOT be used as a unit of potential energy?

gram·cm/s2

Suppose that the fundamental dimensions are taken to be: force (F), velocity (V) and time (T). The dimensions of potential energy are then:

FVT

A golf ball is struck by a golf club and falls on a green three meters above the tee. The potential energy of the Earth-ball system is greatest:

when the ball reaches the highest point in its flight

100

only I, II, and IV are true