Physics of Human Affairs Test #2
Which of the following is NOT a possible energy source for a steam-electric generating plant? a. fossil fuels b. fissionable material such as uranium c. wood d. solar energy e. all of the above are possible energy sources
E
Which of these, if used to replace gasoline as an automobile fuel, would not contribute to global warming?
Electricity from a nuclear power plant
A "wave" could best be defined as
a transfer of a disturbance from one point to another without any corresponding transfer of matter.
A water wave spreading out in a circle across the surface of a pond is an example of
a two-dimensional wave.
Which of the following uses a heat engine? a. gasoline-fueled car b. diesel-fueled car c. electric car d. fuel sell car running on methane e. fuel cell car running on hydrogen f. hybrid car
a,b,f
Which of the following does not travel at light speed? light x-rays infrared waves radio waves actually all of these travel at light speed
actually all of these travel at light speed
Talk-radio station KOOK is at approximately 90 megahertz on the radio dial. This means that KOOK broadcasts
an electromagnetic wave whose frequency is 90 × 106 vibrations/second.
If two electrons are near each other and are moving past each other, the electromagnetic forces they exert on each other will be
both electric and magnetic
Which of the following is an example of chemical energy? a. the energy stored in firewood that has been gathered for buring b. the energy stored in your body, that enables you to do work c. both of the above d. the energy in a stretched rubber band e. the energy in hot steam
c. both of the above
The basic energy resource that fueled the industrial revolution was a form of
chemical energy
A motionless object could have
elastic energy
What form or forms of energy does a falling elastic ball have when it is at its most-squeezed position on the floor, before it begins to rebound [see figure above]?
elastic only
Earth's magnetism arises from
electric currents in Earth's interior.
If you rub a transparency with a tissue to charge both objects and then hold them at rest several meters apart, the forces they exert on each other will be
electrical attraction only
Of the four known fundamental forces, the one that holds electrons into their orbits in atoms is
electromagnetic
J.J Thomson's experiments with a type of invisible beam known as a cathode ray demonstrated that
electrons exist
The force between two bar magnets cannot be due to gravity because
its too strong to be cause by gravity and it can be repulsive; while gravity is always attractive
A single electron flies through the vacuum inside your TV picture tube, from the back to the front side, where it makes a tiny flash when it strikes the inside of the screen. Neglect the force of gravity on the electron. During the electron's motion through the tube..?
no work is done on the electron, which moves at an unchanging velocity
One situation in which the law of conservation of energy is violated is
nonsense--no violations of this law have ever been observed
Two transparency sheets are rubbed with tissue paper and then two the two transparency sheets are held up near each other. This experiment demonstrates that
similarly - charged objects repel each other
Nuclear and fossil fuel generating plants differ in their need for a
smoke-stack.
"Energy" could best be defined as
the ability to do work
A battery's "voltage" is
the amount of energy it gives to each coulomb of electrical charge.
A system's "entropy" is
the amount of microscopic disorganization in the system.
According to the second law of thermodynamics,
the entropy of all the participants in any physical process cannot decrease.
Which of the following is one of the drawbacks of the automobile engine?
the internal combustion engine has all of these drawbacks
There are no known exceptions to
the law of conservation of energy.
The "atomic number" of an element that appears in the periodic table of the elements represents
the number of protons in the nucleus of an atom of that element.
Conventional automobile efficiencies cannot conceivably be higher than about 25%, even with perfect engineering. This is due to
the second law of thermodynamics
Suppose you grasped a cold doorknob and found surprisingly, that this warmed your hand and further cooled the doorknob. This would violate
the second law of thermodynamics
The second law of thermodynamics implies that
thermal energy cannot be entirely converted into non-thermal forms of energy
James Prescott Joule's experiments, such as stirring a container full of liquid, showed that
thermal energy is actually a form of energy
The figure shows two sets of water waves, created by two sources labeled "A" and "B." The solid half-circles represent wave crests from A, and the dashed half-circles represent wave crests from B. Suppose that individual wave crests from either source A or source B alone are 5 mm above the level of the undisturbed water. Then the displacement of the water [above or below the level of the undisturbed water] at the point marked "x" [with the arrow pointing toward it] is
-10 mm
An object having a mass of 1000 kg moves through outer space, far from all planets and stars and far from all gravitational influences, at a speed of 20 km/s (20,000 m/s). How much work is done on the meteor during a time interval of one second?
0 J
The resistance of a 1.0 meter wire of cross section area of 12 mm2 is 3.0 ohms. What is the current flowing in a 3.0 meter of this wire when connected to the terminals of a 6.0 volt battery.
0.67 ampers
You run a 5000 watt clothes-dryer for 2 hours. How many kilowatt-hours of energy did you consume?
10
You push your physics book across a table. The book weighs 8 N, you push with a steady 5 N force, and the force of friction against the book is 3 N. You push the book a distance of 2 m. The amount of work you do on the book is
10 J
You wish to move 125 tonnes of freight a distance of 200 km. How many liters of gasoline are needed to move it by truck, and by rail?
1000 liters and 250 liters
Population growth in a finite environment. Bacteria reproduce themselves by simply dividing. If you start with 1 bacterium, it will divide into 2; they will divide into 4, then into 8, and so forth. Since each population doubling occurs in the same time interval, this is an exponential process. Suppose that some strain of bacteria has a dividing time of 1 minute. You put 1 bacterium into a bottle at 11 A.M, and at noon you note that the bottle is full of bacteria. The bottle was half full at?
11:59
A bag of groceries having a mass of 6 kg and a weight of 60 N falls from a shelf that is 2 m high. Just as it begins to fall, its gravitational energy (relative to the floor) is?
120 J
Two sources of waves, call them A and B, send out waves across the surface of a lake. The waves from A have crests 1 cm high as measured from the normal undisturbed surface of the water. The waves from B are identical to those from A. How far is the water displaced at a point where a valley from A crosses a valley from B?
2 cm downward
Elizabeth lifts a 10 N book from the floor to the table, a height of 2 m. How much work does Elizabeth do?
20 joules
A particular coal-burning generating plant consumes 8000 tonnes of coal per day. Assuming that the coal is pure carbon, which of the following is closest to the amount of carbbon dioxide that this plant injects into the atmosphere every day?
24,000 tonnes
The temperature of a nice day is about
25 degrees C
An engine consumes 400 J of thermal energy while exhausting 300 J has an efficiency of
25%
A 100 W lightbulb has an energy efficiency of 5%. It is turned on for one minute. During this time, the visible radiant energy output of the lightbulb is
300 J.
Suppose a 1 m strand of 1 mm diameter copper wire is attached directly from the negative to the positive terminal of a 6-volt battery. The current in the wire is then
300 amp (1-meter of copper wire having a cross-sectional diameter of 1 millimeter is about 0.02 ohms)
Your radio is tuned to 98 MHz on the FM dial. If the speed of electromagnetic wave is 300,000 km/s, what electromagnetic wave wavelength is your radio receiving,
306 cm
You press a 500 N weight from your shoulders up to arms' length, a distance of 0.8 m, during a period of 2 seconds. How much work did you do?
400 J
A large coal-fired electric generating plant burns about 1000 kg [one tonne] of coal every 10 seconds. About much of the tonne actually goes into producing electric energy?
400 kg
A typical large coal-fired electric-generating plant burns about 1 tonne (1000 kg) of coal every 10 seconds, how much of the tonne actually goes into producing electric energy?
400 kg
U.S oil production grew at 8% per year during 1870-1930. Its doubling time was roughly
9 years
A 1000 kg car is accelerated from rest to 100 miles/hour in 10 seconds. Find the output power of this car. Hint: You may need to use Work = Change in Kinetic Energy
98.8 kW
Why might excess CO2 in the atmosphere heat up the earth?
Because CO2 absorbs, or traps, infra-red radiation.
While a wooden matchstick burns, the energy transformation is?
ChemE--->ThermE + RadE
Robin Hood shoots an arrow from his bow. Beginning just before he draws the bow, the energy transformation is?
ChemE--> ElastE--> KinE
How much kinetic energy does a car have when it moves at 100 km/hr, as compared with when it moves at 50 km/hr?
Four times as much
When the inside of a refrigerator is cooled, does thermal energy flow from hot to cold, or is it from cold to hot? Does this happen spontaneously, or is outside assistance required?
From cold to hot. Since this is against the normal flow of thermal energy, outside assistance is required
In the operation of a hydroelectric power plant, the energy to generate the electricity can be traced to?
GravE in the lake behind the plant's dam and RadE that comes from the sun
Electrical and gravitational forces follow similar equations with one main difference:
Gravitational forces are always attractive but electrical forces can be attractive or repulsive.
Which type of generating plant would you expect to be more energy efficient, steam-electric or hydroelectric?
Hydroelectric, because it is not a heat engine and so is not restricted by the second law of thermodynamics.
Under what condition can a force act on an object and yet do no work on that object?
If the object does not move
When you send a wave pulse down a rope or Slinky, it eventually dies out. What has become of the energy?
It was transformed into thermal energy.
Jed leans against a brick wall while Ned pushes hard against it and "works up" a sweat in the process. Is either Jed or Ned doing any work on the wall according to the picture?
Neither one is. (The wall isn't moving so there isn't work exerted on the wall)
Is a fuel-cell vehicle properly described as a "heat engine"?
No, because it converts chemical energy directly to electric energy.
Does the growth of a leaf violate the law of entropy, and why or why not?
No, because the increase in the entropy of the radiation passing through the leaf is greater than the decrease in the entropy of the leaf itself.
The energy transformation during photosynthesis is?
RadE--> ChemE
The force that is exerted by electrons by a magnet as it picks up iron nails could be best described as
The magnetic force exerted by electrons moving within the magnet, on the electrons moving within the nails
Which one of the following is the correct statement regarding the resistance?
The resistance of a wire is directly proportional to the length of the wire.
Which law of physics, if any, distinguish between the backward and the forward direction in time?
The second law of thermodynamics but not the law of conservation of energy
A charged rod carrying a negative charge is brought near two spheres that are in contact with each other but insulated from the ground. If the two spheres are then separated, what kind of charge will be on the spheres?
The sphere near the charged rod becomes positive and the other becomes negative.
An operating lightbulb transforms ElectE into?
ThermE and RadE
When you touch a piece of ice,
Thermal energy flows from your hand to the ice
Are small ripples sent out across the surface of a lake truly "waves", as that word is used in physics?
Yes, because the water itself doesn't go anyplace but simply oscillates up and down.
Two brief waves or "pulses" are sent down a rope, in opposite directions, as shown in the figure. Pulse A is 1 cm in height, and pulse B is 2 cm in depth. When they meet, they will create
a disturbance 1 cm deep
Since there has never been an observed violation of them, we can say that the principles of energy are?
a good theory
Which of these uses thermal energy to do work?
a hot air balloon
Chemical energy is transformed into gravitational energy when
a person walks uphill
A neutral atom loses one of its electrons. It is then
a positive ion.
A gas can containing a gallon of gasoline is stored in a basement. This gasoline contains
energy
One car is traveling twice as fast as a second car. How much more work can the first car do. compared to the second car, in smashing into a brick wall?
four times as much
Which part of the electromagnetic spectrum has the shortest wavelength?
gamma
Which of these energy transformations best describes the overall operation of a hydroelectric power plant?
grav E electromag E
The energy transformation that occurs during downhill skiing is
grav E kin E + therm E.
Physically, the type of energy represented by the water behind a dam is,
gravitational
compared with the efficiency of a typical steam- electric generating plant, the efficiency of a typical hydro- electric generating plant is
greater because a hydro-electric plat is not a heat engine and so it does not have the large inefficiency implied by the second law of thermodynamics
X-ray radiation typically comes from
higher-energy electrons orbiting the nucleus in atoms.
The sub-atomic particle known as the "neutrino" was originally hypothesized
in order to preserve the law of conservation of energy in a certain type of nuclear process
When the current through a resistor is increased by a factor of 4, the power dissipated by it
increases by a factor of 16.
A fundamental physical reason for the bicycle's high efficiency as a transportation device is
it is a wheeled vehicle. it is not a heat engine.
A low-power source of energy could put out a lot of work provided it
operated for a long time
A key step in the destruction of ozone by chlorofluorocarbons is
radiation from the sun separates chlorofluorocarbon, resulting in free chlorine.
When the distance between the two charges is doubled, the force between them is
reduced by a factor of 4.
The figure above shows a marble rolling freely back and forth along a curved track. The track is positioned vertically. Assuming no friction and no air resistance, the total energy of the marble
remains the same when the marble rolls from A to B.
Suppose you charge two transparencies by rubbing and then hold them near each other but not touching. Regarding the electric and magnetic forces they exert on each other,
they will exert electric forces but not magnetic forces.
If you saw off one end of a magnet, you will have
two magnets
the "efficiency" of a heat engine is defined to be
work output dived by thermal energy input
Is a block of wood sliding to a stop along a tabletop an "irreversible" process?
yes
When a tablespoon of salt mixes with a quart of water, does entropy increase?
yes
Suppose you slowly, and at a constant speed, lift a 12 N book from the floor to a shelf 2 m above the floor. While you are lifting it, the net force on the book is?
zero