Homework Questions

A satellite is traveling around the earth in a circular orbit. It briefly fires its rocket engine to increase its speed in the forward direction; it is suddenly going faster but its direction of travel didn't change. As a result of this speed increase, the orbiting satellite's average distance from the center of the earth

remains the same and the orbit remains circular.

remains the same, but the orbit is nol longer circular.

increases.

decreases.

c

How does current flow in the depletion region of a diode?

flows from positive to negative only

no current flows

flows in either direction

b

Microwaves travel ______ visible light waves.

at the same speed as

at a slower speed than

at a greater speed than

a

Power is

The amount of heat generated when a job is done.

The measure of how quickly work is done on an object.

The amount of energy used multiplied by time.

The amount of energy used to do a particular job.

b

What does a diode do?

Amplify current

Stores charge

Impedes current

Allows current to flow in only one direction.

d

Astronauts in the space shuttle feel weightless because

there is no atmosphere where they are.

they are moving very rapidly.

they are in a constant state of free fall.

they are so far away from the center of the Earth.

c

When a rocket leaves earth's atmosphere, there is no longer any air near it. Is the rocket still able to obtain forward thrust and, if so, what is pushing it forward?

No, it cannot obtain forward thrust when there is no nearby air to push against.

Yes, the earth pushes it forward.

Yes, its exhaust gases push it forward.

Yes, earth's atmosphere still pushes it forward.

c

A ball hits a wall going 10 m/s, and bounces off going 7 m/s. The coefficient of restitution is

0.70

-17 m/s

0.49

1.41

a

A baseball player throws a bat up in the air, so that it spins as it translates. The bat will rotate about its

pivot point farthest from the handle

long axis

pivot point near the handle

center of mass

d

A car stereo draws 1 A of current at voltage 12 V. What power does it use?

288 W

2 W

12 W

120 W

c

A charged object is able to attract

only charged objects

only neutrons

neutral objects but not neutrons

c

A child is riding a bike and skids to a stop. What happens to their kinetic energy?

It is conserved.

It is turned into potential energy.

It is turned into heat by sliding friction.

It is dissipated by static friction.

c

A child throws a ball perfectly horizontally at the same time a dirt clod falls off it at the same height above the ground. The clod falls vertically downward. Ignoring air resistance, the time when the clod hits the ground will

be earlier than when the ball hits

not depend upon how high it started falling from

be equal to the time the ball hits the ground

be later than when the ball hits

c

A diaphragm is used to increase a lens' effective diameter. What effect does this have on the lens' f-number?

It increases.

It decreases.

Not enough information is given to determine.

It remains constant.

b

A gymnast jumps upward with an initial speed of 10m/s. She is in the air for a total time of

10 seconds

1 second

2 seconds

4 seconds

c

A nearsighted person's eyes

refract light too much and focus images of distant objects in front of the retina.

refract light too little and focus images of distant objects in front of the retina.

have pupils that are too small.

refract light too much and focus images of distant objects behind the retina.

a

A pedestrian bridge crosses a street. This bridge is entirely supported by columns from below. A gap at each end of the bridge separates the bridge's surface from the sidewalks leading to the bridge. The width of each gap changes with time. This width is largest

at midnight.

at noon.

on hot days.

on cold day.

d

A photoconductor's electrical properties go from insulating to conducting when it is exposed to light because,

light supplies the energy needed to move electrons from the valence band to the conduction band.

light lowers the energy of the conduction levels eliminating the energy gap.

light allows extra electrons to move out of the valence band giving the semiconductor a positive charge.

light allows extra electrons to move into the conduction band giving the semiconductor a negative charge.

a

A projectile is thrown directly upward and caught again. At the top of its path

its vertical velocity is zero

its acceleration changes

it stops accelerating

its horizontal velocity changes

a

A radio tuner works because

the capacitor dimensions must be the same size as the signal wavelength.

the magnetic field in the inductor must be the same size as that of the signal.

the electric field in the capacitor must be the same size as that of the radio signal.

the charge sloshes back and forth in the tank circuit at a certain frequency and the station being tuned in to must be very near that frequency.

d

A spinning Frisbee is thrown between two persons in a park. The motion of the Frisbee is

rotational and translational.

purely rotational.

neither rotational nor translational.

purely translational.

a

A step-up transformer has 20 primary turns and 1200 secondary turns. If the primary voltage is 10 V, what is the secondary voltage?

600 V

48000 V

200 V

2400 V

a

A transformer provides the 12,000 volts needed to operate the neon sign in a local convenience store. When AC current flows through the transformer's primary coil and experiences a voltage drop of 120 volts, current flows through the transformer's secondary coil and experiences a voltage rise of 12,000 volts. Based on this observation, it is likely that

the current in the secondary coil is about 100 times as large as the current in the primary coil.

the primary coil has about 100 times as many turns in it as the secondary coil.

the secondary coil has about 100 times as many turns in it as the primary coil.

the currents in the two coils are about equal.

c

A typical bar magnet has an "N" stamped on its north pole end and an "S" stamped on its south pole end. With the right tools, you might be able to change this bar magnet in one or more of the following ways: (1) remove its magnetic poles altogether, (2) reverse its magnetic poles so that it has a north pole at the end stamped "S" and a south pole at the end stamped "N", (3) convert its north pole into a south pole so that it has south poles at both ends and no north poles. Which of those three options is physically possible?

Only (2) and (3)

None of them is possible.

All three are possible.

Only (1) and (2)

d

An 800 kg car moving at 1 m/sec to the right strikes a 400 kg car moving to the left. If the cars stick together and stop moving right after the collision, what was the velocity of the 400 kg car?

8 m/sec to the left

2 m/sec to the left

It was stationary

4 m/sec to the left

b

An FM radio station instructs your radio receiver how to move its speaker cone by varying the

strength of the electric and magnetic fields in the radio wave it produces.

amount of electric charge it pushes up and down its antenna.

frequency of the radio wave it produces.

amplitude of the radio wave it produces.

c

An object experiences a net force of 40 N and has an acceleration of 4m/s2. The object's mass must be

40 kg

5 kg

10 kg

20 kg

c

An object is very far from a converging lens with a short focal length. Where does the image form?

No image forms.

Far from the lens

On the same side of the lens as the object

Close to the lens

d

Around high tension power lines there are

neither electric nor magnetic fields.

electric, but no magnetic fields.

magnetic, but no electric fields.

both electric and magnetic fields.

d

At various times in the news it has been reported that certain vehicles are susceptible to rolling over. The physical mechanism that is responsible for rollovers is

Frictional torques from the road on the veichle about its center of mass.

Strong air currents simply blowing the veichle over.

Frictional torques about the driver only.

Frictional torques from the veichle on the road acting below the road's center of mass.

a

A postive charged cloud passes overhead during a thurnderstorm.

What direction does the electric field point?

left

up

down

right

c

Commercial electric power is sent across country using high voltage transmission lines. If low voltage transmission lines were used instead, those low voltage lines would

have to use direct current, which would not operate most equipment properly.

have to be made of thicker metal, which would be expensive.

not be magnetic enough to transform electricity efficiently into energy.

have to placed closer to the ground, where they would be more hazardous.

b

Consider a 100 kg Father and his 50 kg girl. They decide to enjoy balancing on a seesaw, which is a uniform board 2 m long and pivoted exactly at its center. If girl sits at the seesaw's end (1 m from the center), how far from the center on the other side should the father sit?

0.4 m

1.0 m

Farther out than the board will allow.

0.5 m

d

Driving down the road, you hit an insect. How does the force your car exerts on the insect compare to the force the insect exerts on the car?

The force the car exerts on the insect is less.

The force the insect exerts on the car is less.

The two forces are equal in magnitude.

The insect exerts no force on the car

c

For an appliance to receive and consume electric power,

it must magnetize the current with its electric field.

a current must flow through it across a voltage decrease.

it must polarize the current with its magnetic field.

a current must flow through it across a voltage increase.

b

For an object that is floating on a fluid,

The weight of the object becomes less than in air.

The weight of the fluid displaced equals the object's weight.

The weight of the fluid displaced is greater than the object's weight.

The weight of fluid displaced is less than its weight.

b

Force and momentum are related in that:

Momentum is a change in force per unit time

Momentum times force equals a constant.

Momentum and force both have the same units

Force is a change in momentum per unit time

d

Friction does NOT depend upon?

the force with which an object is pressing against a surface

the area of contact

the type of surfaces in contact

whether the contact surface is wet or dry

b

Housing and natural animal insulation works because

the insulating materials trap air and prevent convection.

the insulating materials prevent radiation

the insulating materials are poorer heat conductors than air.

the insulating materials reflect radiation

a

If an electron and a proton both experience the same electric force,

neither will accelerate.

their accelerations will have the same magnitude.

the proton will have greater acceleration.

the electron will have greater acceleration.

d

If you are backing up and slowing down, your acceleration is directed

to the left

forwards

backwards

nowhere

b

If you double the absolute temperature of a light bulb filament, its power output increases by a factor of

8

4

16

2

c

If you double the absolute temperature of a star, its power output increases by a factor of

2

16

8

4

b

If you double the radiating surface area of a star, its power output increases by a factor of

2

8

4

16

a

Imagine being an observer watching a light wave travel by you, much like you would watch a car travel by you on the highway. If you could detect the electric field at your location, you would observe

the electric field remaining constant because light does not carry charge.

no electric field at all.

the electric field undulating to the right or left as the wave travels to the right or left.

the electric field undulating up and down as the wave travels to the right or left.

d

Imaging x-rays go easily through living tissue but not so easily through bone. This is primarily because the calcium atoms in bone have

an odd number of electrons while those in tissue have even numbers of electrons.

many more neutrons in their nuclei than the atoms in tissue have.

an even number of electrons while those in tissue have odd numbers of electrons.

many more electrons than the atoms in tissue have.

d

In a typical laser, the right color of light bounces back and forth between two mirrors and

is amplified by the mirrors.

is amplified by the excited atoms in the laser medium.

is de-amplified by the laser medium.

is ignored by the laser medium.

b

In order to do a positive amount of work you must

exert a force or move

exert a force and move

exert a force and move in the opposite direction of the force

exert a force and move in the direction of the force

d

It is important for cyclists to lean their bicycles while negotiating sharp turns because

they increase their static stability

their tires flatten out, thus getting better traction on the road.

the torque created by their leaning balances out their weight and holds them up.

the torque created by their leaning balances out the frictional torque from the road which would tend to flip them.

d

Lead sinkers actually float on the surface of liquid mercury. Which takes up less space: 1 kg of mercury or 1 kg of lead?

Neither take up any space

Mercury

Not enough information is given

Lead

b

Light passing from air into a denser transparent medium will

not change speed.

slow down.

Not enough information is given to determine.

speed up.

b

Like a baseball bat, a tennis racket has a sweet spot at its center of percussion. If a tennis ball hits this center of percussion, the racket's handle does not accelerate. This is because

the racket's velocity doesn't change when the ball hits its center of percussion.

the racket's center of mass accelerates backward while its handle rotates forward about its center of mass and the two motions cancel one another at the handle.

an impact at the center of percussion transfers no momentum to the racket and doesn't cause the racket to accelerate.

an impact at the center of percussion exerts no torque about the racket's center of mass and doesn't cause the racket to undergo angular acceleration.

b

Many sophisticated cameras have zoom lenses. When you select the telephoto setting, the objects in front of you appear much closer. In this setting,

the aperture of the lens is larger than normal.

the aperture of the lens is smaller than normal.

the focal length of the lens is longer than normal.

the focal length of the lens is shorter than normal.

c

Microwaves can't get through the metal screen in a microwave oven, but light can because

the wavelength of microwaves is about the same size as the holes.

the wavelength of visible light is about the same size as the holes.

the screen acts like a resistor, absorbing the microwaves and not reflecting them.

light travels faster than microwaves.

a

Microwaves have

higher frequencies than visible light

comparable frequencies to visible light

no frequency at all

lower frequencies than visible light

d

Microwaves have wavelengths between

1 millimeter to 1 meter.

1 micrometer to 1 millimeter.

1 meter to 1000 meters.

1 micron to 100 microns.

a

People fighting forest fires carry emergency tents that have shiny aluminum outer surfaces. If there is trouble, a fire fighter can lie under the tent to block the heat from burning trees overhead. The tent helps because

conduction carries heat downward toward the fire fighter and the aluminum tent conducts that heat harmlessly into the ground.

radiation carries heat downward toward the fire fighter and the aluminum tent reflects most of that radiation.

both conduction and radiation carry heat downward toward the fire fighter and the aluminum tent blocks most of that heat.

convection carries heat downward toward the fire fighter and the aluminum tent blocks most of the heat carried by convection.

b

Sunsets are a deep red because

most polluting gases and dust particles in the air are reddish in color and lend their color to that of the sky.

tiny particles in the air are more efficient at scattering short wavelength light than they are at scattering long wavelength light. Hence, long wavelength light ends up coming directly towards you.

air molecules absorb red light more efficiently than they do blue light because of their electron orbitals.

air molecules absorb blue light more efficiently than they do red light because of their electron orbitals.

b

Suppose you are a football player and you kick a ball for a field goal. Ignoring air resistance, the ball's horizontal velocity

is zero at the top of the path

changes throughout the path due to gravitational acceleration

is maximum at the top of the path

remains constant throughout the path

d

Suppose you are riding on a merry - go - round and you move out to the edge. Why does the rotational rate of the system decrease?

There was a net force on the entire system, slowing it down.

Angular momentum is conserved and the rotational mass decreased

There was a net torque on the entire system, slowing it down.

Angular momentum is conserved and the rotational mass increased.

d

Suppose you are standing on a bathroom scale when you are flying in a jet airplane. For a moment the scale reads less than your actual weight. During that moment, it's exerting an upward force on you that is less than your weight and you are

accelerating downward.

accelerating sideways.

not accelerating.

accelerating upward.

a

Suppose you have an aquarium and you notice that you have a solid plastic decoration and a rock of about the same volume but twice as dense, and both are totally submerged in the water. The buoyant force on the plastic object is about ___________as that on the rock.

the same.

half as big.

twice as big.

one quarter as big.

a

Suppose you have two cars, and the larger one is twice as massive as the smaller one. If you and a friend push on them so that their accelerations are equal, how must the forces applied to the cars compare?

The force on the larger car is equal to that on the smaller car

The force on the larger car is twice that on the smaller car.

The force on the larger car is more than three times that on the smaller car.

The force on the larger car is that on the smaller car.

b

Suppose you push horizontally on the wall of a building. For you to do positive work on the wall, which of the following need to happen?

the wall lifts up

b and c

the wall moves away from you

the wall moves sideways

c

Suppose you take off in a car with your physics book on top. If you are accelerating forward and the book rides with you, in what direction does friction act on the book?

forwards

backwards

There is no friction since there is no sliding.

The force of friction is infinite.

a

Suppose your car's speed triples. By what factor will its kinetic energy change?

No change

Impossible to know.

Three times greater

Nine times greater.

d

The energy that is released by a nuclear weapon was put into the weapon's fissionable core in the process of

separating the core's fissionable nuclei from the non-fissionable nuclei with which they are normally found.

raising the core's fissionable materials from deep in the earth where they were mined.

assembling each of the core's fissionable nuclei from smaller nuclear pieces.

heating and melting the fissionable materials when the core is being fabricated.

c

The fallout from a nuclear explosion and the waste from a nuclear reactor contain radioactive isotopes. The atoms of these isotopes

emit a steady stream of X-ray radiation.

have unstable nuclei but are chemically indistinguishable from stable atoms.

are chemically unstable but their nuclei are indistinguishable from stable atoms.

have unstable nuclei and are chemically unstable.

b

The fallout from a nuclear explosion and the waste from a nuclear reactor contain radioactive isotopes. For example, iodine-131 (a fission byproduct) is radioactive while iodine-127 (normal iodine) is not. An atom of iodine-131 differs from an atom of iodine-127 because the iodine-131 atom has more

gamma rays in its nucleus.

electrons in its orbitals.

neutrons in its nucleus.

protons in its nucleus.

c

The speed of light is roughly 300,000,000 m/s. A radio station has frequency 300 megahertz. What is the station's wavelength?

1 meter

30,000,000,000 meters

1,000,000 meters

33 meters

a

The velocity of an object is equal to

the rate of change of its speed

the time an object has been in motion

the rate of change of its position

the rate of change of its acceleration

c

Thomas Edison's dominance in the electric power industry was struck a serious blow when his competitors, Nikola Tesla and George Westinghouse, began to use transformers with their alternating current (AC) electric power systems. Edison was unable to use transformers in his direct current (DC) electric power systems because

a transformer requires changing currents in its coils in order to transfer power between those currents.

DC electric power must flow through thicker wires than can be used efficiently in transformers.

direct current electric power must flow directly from the generator to a home, without passing through any intermediate devices.

Tesla and Westinghouse held the U.S. patent rights to transformers and prevented Edison from using them.

a

Ultraviolet light causes damage to your skin while infrared light does not because

ultraviolet light has more photons than infrared light.

ultraviolet light has a longer wavelength than infrared light.

ultraviolet light is more intense than infrared light.

a photon of ultraviolet light carries much more energy than a photon of infrared light.

d

What is needed for a nuclear chain reaction?

Infinite mass

Critical mass

Subcritical mass

Supercritical mass

b

What is the potential energy of a 5 kg box that is 6 m above the ground?

30 J

300 J

50 J

600 J

b

What occurs whenever a charged particle accelerates?

Bremsstrahlung

X-ray fluorescence

Characteristic x-rays

Compton scattering

a

What percentage of an atom's mass is in its nucleus?

Over 99.9%

Over 99% but less than 99.9%

Over 90% but less than 99%

Less than 90%

a

What type of friction causes bearings to not waste much energy?

Both

Neither

Sliding

Static

d

When a baseball player hits a ball, the bat can respond by

rotating.

any combination of rebounding, vibrating and spinning.

vibrating.

rebounding.

b

When an x-ray photon is absorbed in a tumor, it may cause the tumor cell to die because the photon

magnetizes the cell and causes it to stick to passing killer cells of the immune system.

polarizes the cell and causes its vertical electric field to become horizontal.

causes the cell to crystallize into a brittle solid that cannot tolerate any deformation.

carries enough energy to damage molecules and cause chemical injury to the cell.

d

When building soap box cars which race by coasting downhill it is better to have solid wheels rather than ones of equal mass with spokes because

The solid wheels have a lower rotational mass and therefore accelerate faster.

The solid wheels have a higher rotational mass and therefore retain more rotational energy.

The wheels with spokes lose too much energy by heating up the air.

The solid wheels are easier to paint.

a

When chewing hard nuts, we use the teeth towards the back of our mouth because we are able to exert a greater _____________ on the nuts.

lever arm

angular velocity

force

torque

c

When sitting still on the ground, a tricycle is in a state of

unstable static equilibrium

unstable dynamic equilibrium

dynamic equilibrium

stable static equilibrium

d

When uranium undergoes fission, it releases an enormous amount of energy. That energy was stored in the uranium nuclei as

electrostatic potential energy—from the electrostatic forces between nucleons.

kinetic energy in the nucleons.

gravitational potential energy—from the gravitational forces between nucleons.

nuclear potential energy—from the nuclear forces between nucleons.

d

When using a magnifying glass to focus the Sun onto a piece of paper, the distance from the lens to the paper should be

Not enough information is given to determine.

equal to the focal length of the lens.

greater than the focal length of the lens.

less than the focal length of the lens.

b

When you drop a strong magnet through the center of a copper pipe, the magnet

descends rapidly because its motion causes currents to flow in the pipe and those currents attract the magnet.

descends slowly because its motion causes currents to flow in the pipe and those currents repel the magnet.

descends slowly because it is attracted to the magnetic copper metal.

falls at the usual rate because copper metal is nonmagnetic.

b

Which answer has the colors in order from the highest energy to the lowest?

Red Green Blue

Blue Green Red

Red Blue Green

Blue Red Green

b

Which of the following devices on a car can be used to cause the car to accelerate?

All the above

The steering wheel

The gas pedal

The brake pedal

a

Which of the following is not ferromagnetic?

Aluminum

Iron

Nickel

a

Which part of a welding flame is the coldest?

The blue part

The orange part

The yellow part

The red part

d

Which temperature scale has 100 as the boiling point of water?

Kelvin

Fahrenheit

Celsius

c

White LEDs are

infrared LEDs that heat up phosphors

yellow LEDs with a white coating on the inside.

LEDs that emit white light.

ultraviolet LEDs with phosphors inside.

d

Why are good thermal conductors generally good electric conductors also?

The answer depends on the specific metal.

The molecules in both don't move around very much.

Heat and electricity are the same things.

Electron motion is responsible for determining both properties.

d

Why do elastic balls bounce so well?

They store energy through compression, like a spring.

They are all filled with a special energy-absorbent liquid.

They permanently deform, storing energy.

They are always thrown well.

a

Why does an ice cube feel cold?

Cold from the cube enters your hand by convection.

Cold from the cube enters your hand by conduction.

Heat from your hand enters the cube by conduction.

Heat from your hand enters the cube by convection.

c

You and a friend are spending a weekend at a carnival. You get bored and begin to make electrostatics measurements. It turns out that you have a charge of +3 Coulombs and your friend a charge of +5 Coulombs. What is the net electric charge?

+8 Coulombs

+2 Coulombs

-8 Coulombs

-2 Coulombs

a

You are flying on an airplane and you notice that a ball of aluminum foil from lunch starts to roll to the left. From the motion of the foil ball you can conclude that the plane is

moving at constant velocity toward the left.

turning toward the left.

turning toward the right.

moving at constant velocity toward the right.

c

You are playing with your younger cousins and find yourself on all fours, with your hands and feet on four bathroom scales on the level ground. You took a "Physics in Everyday Life" course so you can make a reasonable guess that the reading on each scale is obtained by

your mass.

dividing your weight by 4.

dividing your mass by 4.

dividing your weight by 2.

b

You are riding an amusement park ride where you are strapped to the inside of a giant metal wheel that is rotating quite rapidly. Your acceleration is

Straight up

Toward the center

Zero

Straight down

b

You are riding in a hot air balloon. You have not used the burner for some time and the balloon begins to sink. Assuming that no air is allowed to leave or enter the balloon,

the average density of the balloon remained constant and the buoyant force on the balloon became less than its weight.

the balloon became heavier.

the average density of the balloon became greater than the surrounding air and the buoyant force on the balloon became less than its weight.

the average density of the balloon became greater than the surrounding air and the buoyant force on the balloon remained constant.

c