SCIENCE LEVELED EXAMS 03
SCIENCE LEVELED EXAMS 03 -
- HARD
1.
E In elastic collisions, none of the energy is lost in
deformation of the objects. Therefore, elastic collisions
conserve energy. Elastic collisions, along with inelastic
collisions, also conserve momentum. Thus, elastic collisions
conserve both energy and momentum, while inelastic
collisions only conserve momentum. [USRG:22,1,4]
2.
E Both mass and charge are inherent properties of objects.
These properties must be tied to an object and cannot exist
as independent entities in space. That is, a charge must be
carried by an object, it cannot exist by itself. [USRG:38,1,2]
3.
C According to Snell’s law, the angle of refraction as light
passes from medium 1 to medium 2 can be found by
considering the angle of the light ray in medium 1 and the
indices of refraction for both mediums. In equation form,
n1sin.1 = n2sin.2. Thus, the closer the indices of refraction
are for mediums 1 and 2, the less the angle of light travel
will change. Glass has an index of refraction of 1.5, which
is most similar to 1.45, the index of refraction for oil.
[USRG:30,2; USRG:35,1; USRG:35,2,1]
4.
A Recall that current flows in the opposite direction of
electron flow by convention. Thus, the current flows to the
right in this scenario. Using Right Hand Rule 1, point the
thumb to the right, then curl the remaining fingers. At the
top of the wire, the fingers point forwards. Therefore, the
magnetic field lines point forwards at that point. Note that
while distance from the wire does impact the strength of
the magnetic field, it will not alter the direction of the
magnetic field. [USRG:44,2,2; USRG:51,1,2]
5.
D Studies of dynamics focus on the causes of motion. Sir
Isaac Newton was the first scientist to focus on dynamics,
and he determined three laws about the causes of motion.
[USRG:15,1,2]
6.
D Using Right Hand Rule 2, the thumb must follow the
electron’s motion and point right while the index finger
follows the field lines and points forward. This leaves the
middle finger directed down for the force. The electron,
though, has a negative charge. This charge means that the
direction of the force must rotate 180° and point upwards.
[USRG:52,1,3]
7.
C A wave’s wave velocity equals its frequency times its
wavelength. It measures how rapidly the wave as a whole
propagates through its medium. In this example, 20 Hz
times 5 m equals a wave velocity of 100 m/s. [USRG:28,2,4]
8.
A Energy cannot be created or destroyed in any system,
although it can be transformed into a different form or
transferred. Conservative force, by definition, does not alter
an object’s energy. Although work is defined as force times
distance traveled, an alternate equation is W = .KE. The
conservation of momentum, however, does not indicate
conservation of energy. In inelastic collisions, while
momentum is conserved, energy is not. [USRG:18,1,4; USRG:19,2,1;
USRG:19,2,2; USRG:22,1,4]
9.
E A common unit system is the SI system. SI stands for
Système International, or in English, International System of
Units. The SI system is easily to use because the different
units are related to one another by factors of 10. [USRG:6,1,2]
10.
A The coulomb force occurs between two separated charged
objects. It equals the charge of object 1 times the charge of
object 2 times the electrical constant, all divided by the
distance between the two charged objects squared. Like
gravitational force, the coulomb force is inversely related to
the distance squared. The coulomb force, however, is
significantly stronger than the gravitational force. [USRG:39,2,1]
11.
E Circular motion is more complex than linear motion. The
variables that are used in linear kinematic equations are
modified to include the object’s shape for circular motion.
The analogous variable for force is torque. Torque can be
found using the equation rF. [USRG:24,2,4]
12.
E
Longitudinal waves are waves where displacement occurs in
the same direction of the wave’s motion. This displacement
occurs in the form of a fluctuation in density or pressure in
the medium. A common example of a longitudinal wave is
the sound wave. Please note that light waves, which classify
as electromagnetic, are transverse waves. [USRG:30,2,2]
13.
B
Magnets produce fields that are represented by field lines.
Field lines close together indicate a strong magnetic field.
In bar magnets, the field lines leave the magnet at the
north/positive pole and reenter at the south/negative pole.
The field lines also pass through the magnet, traveling from
the south to the north pole. In theory, the field lines
represent the effect of a positive monopole. Due to electron
spinning, however, monopoles do not actually exist. The
field lines represent a theoretical force. [USRG:51,2,3; USRG:52,1,0]
14.
D In 1820, Hans Christian Oersted discovered that placing a
compass near a current carrying wire moves the compasses
needle. This observation implied magnetic activity from an
electric current. Previously, electricity and magnetism were
thought to be entirely unrelated. In light of Oersted’s work,
that view was questioned. Many years later, in 1864, James
Maxwell linked electric and magnetic activities more
completely using four equations. [USRG:50,2,1]
SCIENCE LEVELED EXAMS 03 PAGE 10 OF 12
DEMIDEC ©2011
15.
A Young’s experiment directs light through two closely placed
slits, essentially creating two light sources a small distance
apart. In doing so, the setup enables researchers to study
path length differences and the subsequent wave
interference. Young’s experiment produces alternating
bands of brightness and darkness, corresponding to regions
of constructive and destructive interference. [USRG:32,1,0]
16.
A
Position is defined as the location of an object relative to
the origin. Displacement, on the other hand, is the change
of position over a give time frame. This value eliminates the
dependence of the origin via subtraction of initial position
from final position. Since distance, velocity, and
acceleration are all calculated from displacement, they are
also independent of the location of the origin. [USRG:10,1,3;
USRG:10,1,4; USRG:10,1,5; USRG:10,2,2; USRG:10,2,5]
17.
A
Conservative forces do not alter the energy of an object’s
energy. They may convert the energy from one form to
another, however. A non-conservative force, on the other
hand, changes the energy on an object. Kinetic friction
reduces the energy found in a moving object, and is a non-
conservative force. Please note that kinetic energy is a scalar
quantity and not a force. [USRG:20,1,1]
18.
A
There are two types of friction – static and kinetic. Static
friction occurs while attempting to move a stationary
object. It varies in proportion to strength of force applied
to the object, although it does have a maximum value.
Once the maximum is reached, the object begins moving
and any friction becomes kinetic friction. [USRG:16,1,2]
19.
A According to Faraday’s law, a change in flux through a
closed conductor, such a wire loop, induces a current. This
current will induce a magnetic field that opposes the
change in flux. If a magnet moves towards a wire loop, it
increases the flux through the loop. The current induced
would aim to reduce the flux through the loop. By Right
Hand Rule 1, this opposition occurs with a counterclockwise current through the loop. [USRG:55,2,1]
20.
A
There are several key kinematics variables. The most basic
is position, which is the distance from the origin. Changes
in position are used to find displacement. Position is the
only variable that depends on the location of the origin.
[USRG:10,1,3]
21.
B
According to Snell’s law, n1sin.1 = n2sin.2, where n
represents the indices of refraction for medium 1 and
medium 2, and . represents the angle from the normal
along which the light ray travels in mediums 1 and 2.
Water has an index of refraction of 1.33, and diamond’s
index of refraction is 2.4. Since diamond has the larger
index of refraction, it must have a smaller angle from the
normal for Snell’s law to hold true. That leaves only 11°
and 0° as options. 0°, however, represents a sine value of 0,
making Snell’s law impossible to calculate. Therefore, 11° is
the only reasonable answer. [USRG:30,2; USRG:33,2,2; USRG:35,1]
22.
D
Kinematics problems use multiple vector quantities. In
vectors, both magnitude and direction are important
factors. Therefore, it is necessary to define a coordinate
system before beginning other calculations. This method
allows vector directions to be assigned without confusion.
[USRG:10,1,2]
23.
A
While placing resistors in series increases the equivalent
resistance, resistors placed in parallel produce a lower net
resistance. Of the two options that place resistors in
parallel, it should be intuitive that more resistors in parallel
will decrease the total resistance by a bigger factor. This
assumption is easily confirmed by some quick calculations.
While two resistors of 1 ohm in parallel produce an
equivalent resistance of 0.5 ohms, three resistors drop the
resistance even further, to 0.33 ohms. [USRG:46,2,3; USRG:47,1,2]
24.
E
Several subatomic particles exist. Almost all of these
particles are either positively charged, like the proton, or
negatively charged, like the electron. The only sub-atomic
particle that lacks a charge is the neutron. [USRG:391,2]
25.
D In 1820, Hans Christian Oersted discovered that placing a
compass near a current carrying wire causes the compass
needle to deflect away from north. This discovery was the
first evidence that electricity and magnetism are related
concepts. Since that time, electricity and magnetism have
been more thoroughly connected, primarily through the
work of James Maxwell. [USRG:51,1,0]
26.
A
The most common path to scientific discovery is through
the scientific method. There, scientists ponder questions,
make and test hypotheses, and analyze the results. Most
often, the results cause the scientist to adjust his or her
original hypothesis. This new hypothesis is subjected to
new testing. After many round of this cycle, some scientific
knowledge may be observed. [USRG:5,2,1]
27.
B In series circuits, the sum of the voltage drops across all
resistors equals the battery induced voltage drop. Also,
Ohm’s law states that .V = IR. In this scenario, the voltage
drop across resistor 1 will equal 15 volts, while the drop
across resistor 2 will equal 5 volts. Totaled, this produces a
potential difference of 20 volts. [USRG:46,1,0; USRG:46,1,1; USRG:46,1,2]
28.
E While conductors have relatively low resistances, insulators
tend to have high resistances. Thus, conductors will have
lower resistances than insulators. Metals make good
conductors. Of the materials listed, the only metal is silver.
[USRG:41,1,4; USRG:41,2,1; USRG:43,2,5]
29.
D
Light rays represent the complex transverse waves of light
that travel in straight lines. These rays start at an object and
radiate outward for an indefinite distance, at least in theory.
In real life, gases or other mediums may absorb they light
rays. Human eyes focus the diverging rays to determine
distance from the original object. James Maxwell
determined that light waves have an electromagnetic
nature. [USRG:32,2,5; USRG:33,1,1; USRG:56,2,0]
SCIENCE LEVELED EXAMS 03 PAGE 11 OF 12
DEMIDEC ©2011
30.
D Energy is found via the equation 1/2mv2. The units for
energy are joules, and they also equal kilograms times
(meters per second)2. [USRG:18,2,2]
31.
E
It is often difficult to draw field lines going into the paper.
The symbol X is currently used to draw such lines. The use
of this symbol eliminates confusion over whether or not the
field lines are in the plane of the sheet of paper. [USRG:52,2,3]
32.
C
Total Internal Reflection occurs when the angle of
refraction directs the incident light ray back into the
original medium. This can occur when light passes from a
slower medium to a faster medium. Fiber optics technology
uses this behavior to send data. [USRG:35,1,0]
33.
D
Magnetic behavior originates with spinning electrons. In
some materials, the spins of the electrons total fro produce
appreciable magnetic behavior. These materials classify as
ferromagnetic and include some metals, like iron. [USRG:53,1,2]
34.
A According to Kirchhoff’s loop rule, the sum of all the
potential changes across any closed circuit loop must equal
0. Essentially, this rule states that a circuit loop can neither
create nor destroy electric potential, making this rule an
application of the conservation of energy. [USRG:47,2,2]
35.
E
A medium’s index of refraction is found by dividing the
speed of light in a vacuum by the speed of light in the given
medium. Large indices of refraction indicate a slow
medium, while indices closer to 1 indicate a fast medium.
Oil has an index of refraction equal to 1.45. [USRG:30,1,3;
USRG:35,1]
36.
A Sound waves propagate as a change in density or pressure.
When the medium through which a sound wave travels has
closely placed particles, the sound wave can spread quickly.
In other words, denser mediums carry sound more rapidly
than less dense mediums. Helium, which is a gas, has the
least dense particles. Accordingly, sound waves will travel
slowly through helium. [USRG:30,2,2]
37.
A In parallel circuits, the voltage drop across each resistor
equals the voltage difference established by the battery.
According to Ohm’s law, .V = IR. Therefore, in this
circuit, 20 volts divided by 10 amperes indicates a
resistance of 2 ohms. Note that the resistance of resistor 1 is
irrelevant to this calculation, because the current running
through the other branches of the circuit will differ from
the current flowing through the branch of interest.
[USRG:46,2,6; USRG:47,1,0]
38.
C
Human eyes can perceive light rays with wavelengths
ranging from 400 to 700 nm. Red has the longest
wavelength while violet has the shortest wavelength.
Human eyes are most sensitive to yellow-green light with a
wavelength of 560 nm. [USRG:30,1,2]
39.
D
To add vectors, place the tail of the second vector at the
head of the first vector. In this set-up, vector B points east
from a point 3 meters north of the origin (the head of
vector A). Therefore, vector C will point northeast. Some
simple right triangle math confirms that the length of the
vector is 5 meters. [USRG:8,2,4]
40.
D
There are three basic units that describe all the
measurements, when used in combination. These units
include mass, length, and time. Any other unit is a
combination of some or all of those three units. For
instance, velocity uses the combination of length per time.
[USRG:6,1,3]
41.
E Kinematics calculations revolve around four key equations.
Any given equation contains four of the five kinematic
variables (displacement, time, initial velocity, velocity at a
given time, and acceleration). All of the equations,
however, include initial velocity as a variable. Therefore, in
any calculation, initial velocity must either be known or be
calculated. [USRG:11,2]
42.
C
Wave variables depend on the nature of the medium, the
wave source, or some combination of the two. Frequency
depends only on the rate of the wave source. On the other
hand, amplitude depends on both the force of the wave
source and the nature of the medium. [USRG:29,1,2]
43.
C According to Faraday’s law, a changing magnetic flux
through a wire loop will induce a current in the wire. This
current is driven by a potential difference, or an
electromotive force. The current will also induce a new
magnetic field in opposition to the change. [USRG:54,1,3]
44.
C
Kinetic energy refers to energy in the form of motion. To
calculate kinetic energy, use the equation KE = 1/2mv2,
where m represents mass and v represents the object’s
velocity. The equation mgh represents potential energy, ma
represents net force, Fd represents work, and mv represents
momentum. [USRG:18,2,1]
45.
E
Flux is maximized when the field lines are densest within
the area. With bar magnets, field lines are very dense at
both the north and south poles. Still, the field lines are at
their densest within the magnet. Therefore, placing the
magnet within the wire loop will maximize flux. [USRG:52,1,0;
USRG:55,1,2]
46.
C
Potential is often only considered when looking at the
change in potential. If the potential does not change
between points A and B, then the electric field must be the
same at both of those points. Therefore, movement
between the two points had to be perpendicular to the
electric field. [USRG:42,2,0]
47.
A
While some properties of waves depend only on the wave
source, others depend solely upon the nature of the
medium. A few properties depend on both the wave source
and the medium. Amplitude changes based on the nature
of the medium and the amount of force the wave source
applies to the medium. [USRG:29,1,3]
48.
C
Electric potential examines the potential energy of a
charged particle in an electric field without referencing the
value of the test charge. It is found by dividing the electric
potential energy by the test charge. Since the electric
potential energy equals k(q0q1/r), dividing that value by q0
give the equation V = k(q1/r). [USRG:42,1,4]
49.
C
Impulse is defined as force applied over a time period.
Impulse essentially describes how a force changes an
object’s direction. This change in direction, as for example
in a collision, causes a change in momentum. An
alternative definition of impulse is the change in
momentum. [USRG:21,2,2]
50.
D
Beats are heard when two sound sources produce sounds
with slightly different frequencies. The frequency difference
creates a pattern of alternating constructive and destructive
interference that is heard as beats. The frequency of the
beats equals the frequency difference between the two
sounds. Musicians try to minimize this beat frequency
when tuning instruments. [USRG:32,2,5]
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