Name__________________________ Date___________ Per___
Physics I Honors Semester 2 Exam Review
Unit 9: Waves and Sound
Essential questions:
x What is simple harmonic motion? Motion with a restoring force to bring something back through equilibrium. It occurs over
and over in regular time intervals.
x What factors affect simple harmonic motion of a pendulum and a mass-spring system?
For a pendulum: length, gravity…NOT the mass of the bob
For a mass-spring system: k (the spring constant…how stiff the spring is), mass…NOT gravity x
What is a mechanical wave? Any wave requiring a medium for travel
x What distinguishes one mechanical wave from another? How the particles vibrate. For a transverse wave: particles vibrate
perpendicular to wave motion(think doing ‘the wave’ in the football stadium…you stand up and down…wave moves left and
right). For a longitudinal wave: particles vibrate parallel to wave motion (sound).
x How do the different characteristics used to measure waves relate to each other? Characteristics are speed (v), frequency (f),
wavelength (λ), amplitude (A), and period (T). Relationships: v = λf and f = 1/T and T = 1/f
x
x
x
x
x
x
Why does the speed of a wave change passing from one medium to another? Because waves are a transmission of energy.
That energy will travel differently in different materials. FREQUENCY NEVER CHANGES from medium to medium…so
speed and wavelength change to compensate.
What determines whether an incident wave pulse striking a boundary reflects inverted or not? It depends on the boundary. At
FIXED boundaries, reflections are INVERTED. At FREE boundaries, reflections are UPRIGHT.
How can the principle of superposition be used to describe wave interference in a variety of situations? If the waves are both
on the same side of equilibrium will have constructive interference; if on opposite sides of equilibrium will have destructive
interference.
What are characteristics of a sound wave? Sound is longitudinal (like a slinky); sound needs a medium to travel, loudness is
related to amplitude…or how much energy the sound wave has.
Why does the speed of a sound wave change as it travels through different media or changes in the properties of the same
media? Because waves are a transmission of energy. That energy will travel differently in different materials.
FREQUENCY NEVER CHANGES from medium to medium…so speed and wavelength change to compensate.
What is the Doppler Effect and how does it occur? A perceived shift in frequency. It occurs when there is movement
between the sound source and the observer. For example, a train moves toward you blowing its horn. While moving towards
you, you will perceive a higher frequency that is really being emitted because the motion of the train causes the wave crests
to be closer together when they arrive at your ear. The opposite is true when its moving away from you.
Key vocabulary: (I am giving you the shortest possible definitions here…easy to remember…mostly to jog your
memory. If you need more than this…LOOK THEM UP online or in the textbook.)
Simple harmonic motion – motion repeated over and over in
Transverse wave – particles vibrate perpendicular to wave
the same time interval due to a restoring force
motion (like a wave on a rope)
Spring constant – stiffness of a spring (k)
Longitudinal wave – particles vibrate parallel to wave motion
Restoring force – for SHM brings back through equilibrium
(like a slinky)
Period – seconds per cycle/wave (T)
constructive interference - waves meet and add up
Frequency – waves per second (f)
destructive interference – waves meet and subtract
Mechanical wave - requires a medium for transport (all
Doppler effect - shift in frequency because either the sound
waves are mechanical EXCEPT electromagnetic waves)
is moving or the observer is moving or both are moving
Practice:
1.
List 4 examples of systems which exhibit simple harmonic motion.
a) A child on a swing (is like a pendulum, right?)
b) A metronome (used to keep time for musicians)
1
Physical Science Semester 1 Exam Review
c)
Name__________________________ Date___________ Per___
A mass-spring system (like the shocks on your car)
d) The pendulum on a grandfather clock
2.
A spring is stretched to a displacement of 30 cm where it experiences a restoring force F. If the spring is then stretched
to a displacement of 60 cm, what is the restoring force, in terms of F, exerted by the spring?
𝐹 = −𝑘𝑥
If initially F = -k(30), and then we stretch the same spring to 60 cm, it must become 2F = -k(60).
The new force is 2F.
3.
If a 43 N force stretches a spring 0.35 m, what is the spring constant (k)?
Given:
F = 43N
Find: k
x = - 0.35m (make either F or x negative because they work in opposite directions)
𝐹 = −𝑘𝑥
43 = −𝑘(−0.35)
𝑘=
= 122.86 k
= 123 N/m
4.
A 2 kg mass is attached to a vertically hanging spring and then released. The system stops oscillating, and eventually
comes to rest with the mass hanging 12 cm from its equilibrium position. Calculate the spring constant (k).
Given: m = 2kg
Find: k x = - 12 cm = - 0.12m
𝐹 = −𝑘𝑥
Problem is…we don’t have F. DRAW a free body diagram! The
upward arrow is the spring force supporting the mass, -kx. The
downward arrow is the weight of the mass, mg.
SO…
𝐹 = −𝑘𝑥 = 𝑚𝑔
−𝑘𝑥 = 𝑚𝑔
−𝑘(−0.12) = (2)(9.8)
5.
a) Write the equation for the period of a mass-spring system.
𝑚
𝑇 = 2𝜋
𝑘
b) What two variables affect the period of a mass-spring system?
6.
mass
and the spring constant
a) Write the equation for the period of a pendulum undergoing simple harmonic motion.
𝑇 = 2𝜋
b) What two variables affect the period of a pendulum? length and gravity
7.
Frequency and period have a(n)
inverse relationship for simple harmonic motion.
8.
If a pendulum is adjusted so that its frequency changes from 25 Hz to 75 Hz, its period will change from t seconds to
t/3 seconds .
2
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
Here’s why: when period is t seconds, the frequency is 25Hz. Let’s say 25Hz = f. When we change the frequency to
75Hz, we’ve really changed it to 3f. Because frequency and period are INVERSELY related, if f went to 3f, then t must
go to t/3.
9.
Identify the type of wave and all of the labeled parts below:
The wave type is
transverse
.
A: crest
B: trough
C: wavelength
D: amplitude
10.
Describe the motion of the particles in a transverse
wave.
Particle motion is perpendicular to wave motion. Think about a wave on a string…the string itself actually moves up
and down…but the wave…the energy moves left to right.
11.
Describe the motion of the particles in a longitudinal wave.
Particle motion is parallel to wave motion. Think about a slinky that you have stretched out on a table. Pinch 10-15
coils together and you will see a pulse move down the wave. The motion of the wave is in the same direction as the
motion of the individual coils.
12.
Describe the motion of the particles in a surface wave. This particle motion is both parallel and perpendicular to wave
motion. See your textbook…pg. 382…for more information.
13.
A periodic wave has a wavelength of 0.85 m and a speed of 64 m/s.
a) What is its frequency?
Given: λ = 0.85m
v = 64 m/s
𝑣 = 𝜆𝑓
64 = 0.85𝑓
𝑓=
Find: f
= 75.29 f
= 75.3 Hz
b) What is its period?
Given: λ = 0.85m
v = 64 m/s
f = 75.3Hz
Find: T
1
𝑇=
𝑓
𝑇=
= 0.01328
T = 1.33 x 10-2seconds
14.
a) Label the nodes and antinodes shown in the standing wave below using the letter “N” for node and “A” for antinode.
b) There are 5 nodes and 4 antinodes in the standing wave below.
3
Physical Science Semester 1 Exam Review
A
N
Name__________________________ Date___________ Per___
A
N
A
A
N
N
N
15.
Draw two waves that will meet and constructively interfere. Include wave direction arrows!
16.
Draw two waves that will meet and destructively interfere. Include wave direction arrows!
17.
Draw the reflected pulse for the following two scenarios:
a) Draw the appropriate Reflected Pulse on the b) Draw the appropriate Reflected Pulse on the diagram diagram above
for Fixed End Reflection.
above for Free End Reflection.
18.
Sound waves are
longitudinal
waves.
19.
Draw a picture of a sound wave.
20.
a) Calculate the wavelength a 392-Hz sound wave in air (v=343 m/s).
Given: f = 392Hz
v = 343m/s
𝑣 = 𝜆𝑓
343 = 𝜆(392)
Find: λ
4
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
𝜆=
= 0.875 λ
= 0.875m
b) Calculate the wavelength of the speed of sound in copper (v=3560 m/s) of a 392-Hz wave.
Given: f = 392Hz
Find: λ
v = 3560m/s
𝑣 = 𝜆𝑓
3560 = 𝜆(392)
𝜆=
21.
= 9.0816
λ = 9.08m
You are standing on a sidewalk. An ambulance with its siren on approaches then passes by you. How does the sound
change as the ambulance approaches then moves away from you?
On approach the sound you hear is a higher frequency (pitch) that the siren is actually making. When it is directly in
front of you, you hear the actual frequency (pitch), as it moves away you hear a lower frequency (pitch). The pitch never
actually changes…it is just that what you hear changes.
Unit 10: Light
Essential questions:
x Does an object have to produce its own light in order to be seen? Nope…we see the moon…it does not produce its own light!
Luminous bodies (like the sun) produce their own light. Illuminated objects can be seen because they reflect light. This is
basically everything that is not a light source (the moon, you, me, book, trees, cars, etc.). x How is comparing properties of
light waves to mechanical waves helpful in learning about light? Because light waves are indeed waves. They reflect, refract,
diffract, disperse, etc…just like all other waves.
x Why do some light waves pass through a polarized filter and some do not? It depends on how the filter is turned. See the
pictures in the polarization questions that are in the practice section.
x How can polarization be used to improve environmental conditions? There are a variety of different ways we can used
polarized light to improve conditions…scattering aerosols, useful for weather radar, etc. Feel free to research different
applications to expand and enhance your knowledge here.
x What is the speed of light in a vacuum, and why does this speed get a special equation symbol c, instead of using v, for
velocity? vlight = c = 3.00 x 108m/s It gets its own symbol because this value is the only true known constant in the universe.
In every test, under every different condition, the speed of light always measures precisely the same amount. It is special, so
it gets special status.
x What are some similarities and differences between mechanical and light waves? Difference: mechanical waves require a
medium for transmission…they have to have something to travel through; electromagnetic waves DO NOT require a
medium…they can travel through a vacuum (and it’s a good thing…because space is a vacuum…and that’s how the Earth
gets all her energy!). Similarities: everything else; all other wave behaviors that occur in mechanical waves also occur in
electromagnetic waves.
5
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
x
How can we apply the mathematical equations used for mechanical waves to electromagnetic waves? We apply them in
exactly the same way: v = λf (except really here c = λf) and f = 1/T.
x
Why is it important to make observations and record data to help understand and explain the universe around us? We can
learn new things about our planet, our solar system, and our universe. Specifically, this is how Hubble determined that the
universe is expanding…a pretty big discovery.
How does the roughness of a surface affect the light reflecting off the surface into a person’s eyes? This is diffuse reflection.
Diffuse reflection is when the rays do not reflect of a surface parallel to one another. This allows us to see the thing…but it is
not blinding or glaring to us. For example, mirrors, shiny metals, etc…those have specular reflection. You can reflect all the
incoming rays in one path. Diffuse reflection reflects the incoming light rays in different paths so that the object is visible.
How can the ray model of light be used to explain the law of reflection? One ray in…hits the surface and changes
direction…bounces away. The incoming angle is equal to the reflected angle. This is the law of reflection.
x
x
x How are image formation, position, height, magnification, and orientation determined for plane mirrors? Images in plane mirrors
are ALWAYS: upright, same sized (same height and magnification = 1), same distance into the mirror as the object, and virtual.
x How are image formation, position, height, magnification, and orientation determined for spherical mirrors? See ray diagrams.
x How does refraction of light affect what we see? Refraction causes light to bend. Which way it bends depends on whether
it’s moving from a medium with a high speed of light to a lower speed of light or vice versa. The refraction will cause things
to appear in a different position than they really are. For example…when you stand on a boat or dock or bank and look into
the water and see a fish. If you try to grab it the fish is always in a different position under the water than it looked to you
above the water due to light’s refraction.
x How is construction of a lens related to how the lens refracts light? Concave lenses cause light to diverge; convex lenses
cause light to converge. This is important because their image formation is different based on their shape.
x How are image formation, position, height, magnification, and orientation determined for thin lenses? Using the lens and
magnification equations OR using ray diagrams.
reflection – reflection off a surface such that the waves are
reflected in the same direction (think mirrors) Reflection –
Key vocabulary:
change in direction of a wave due to bouncing off of surface
Luminous sources – emit their own light
Refraction – change in direction of a wave due to a change in
Illuminated source – reflect light rather than emitting their
medium
own Polarization – property of electromagnetic waves that
Index
of refraction – (n) ratio of the speed of light in the
describes the orientation of their oscillations
material to the speed of light in a vacuum; optical density.
Diffuse reflection – reflection off a surface such that the
waves are reflected in many different directions Specular
Practice:
1.
List 2 examples each of a luminous source and an illuminate source.
Luminous source: the sun, a lightbulb
Illuminated source: a full moon, a mirror
2.
A concave mirror forms a real image 28 cm away from the mirrored surface. If the object is 13 cm away, what is the
focal length of the mirror?
Given:
di = 28 cm
Find: f (concave mirrors are converging, so f will be positive)
do = 13cm
1 1
1
= +
𝑓 𝑑
𝑑
1
1
1
= + = 0.1126 𝑓 28
13
1
𝑓=
= 0.1126 = 8.88
𝑓
f = 8.88cm
3.
Carson Busses is driving down the road on a sunny day. Reflection of light off the road surface results in a large amount
of polarization and a subsequent glare. Annoyed by the glare, Carson pulls out his Polaroid sunglasses. How must the
6
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
axes of polarization be oriented in order to block the glare? (Note: the lines on the filters below represent the axis of
polarization.)
Use the picket-fence analogy to assist you with your answer!
The glare from the road is light that has been partially polarized already by reflecting off the road. It is reflecting parallel
to the road’s surface and making its way through our NON-polarized glasses, like the drawing on the left above. In
order
to block that glare, we want a transmission axis that is NOT parallel to what is already coming through…if it is leaving
the road in one direction…we want something like what is on the right. Leaves the road in one direction, we block it
with our glasses in the other direction. The reason we know the answer is A, is because think when it leaves the road it
will reflect parallel to the road’s surface…so it will reflect like B…meaning B WON’T block the glare…but A will
block the glare. C and D just don’t make sense…in either case you’d get glare in one eye but not the other…which is
silly.
4.
An object placed 16 cm from a thin converging lens along the axis of the lens produces a real image behind the lens at 7
cm from the lens. What is the focal length?
Given:
di = 7 cm
Find: f (converging lens means f will be positive)
do = 16cm
1 1
1
= +
𝑓 𝑑
𝑑
1 1 1
= +
= 0.2054
𝑓 7 16
1
𝑓=
= 0.2054 = 4.87
𝑓
f = 4.87cm
5.
Think of a material that reflects almost all the light that shines on it, but in which you cannot see your reflection. Is this
diffuse or specular reflection? Diffuse! Most surfaces reflect all that light shined on it…it just isn’t reflected in the
same direction…so it’s diffuse reflection.
6.
Describe the images produced by a flat (plane) mirror using the following choices:
a. Real or Virtual?
Virtual
b. Enlarged or Reduced?
Neither, SAME SIZE
c. Upright or Inverted?
Upright
d. Its location along the principal axis.
Same distance behind the mirror as the object is in front (d i = do)
7.
A light ray strikes a flat (plane) mirror at 42 degrees. What is the angle of reflection?
7
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
42 degrees
The law of reflection states that Θi = Θr
8.
In the spaces provided below, describe the image that will be formed when an object is placed in the locations listed.
The description should include whether the image is: a. Real or Virtual
b. Enlarged or Reduced
c. Upright or Inverted
d. Its location along the principal axis.
Convex Lens
Object Location
Image Description
Concave Mirror
Object Location
beyond 2F
a. real
b. reduced
c. inverted
d. between f and 2f
beyond C
a. real
b. reduced
c. inverted
d. between f and C
@ 2F
a. real
b. same size
c. inverted
d. at 2f
@C
a. real
b. same size
c. inverted
d. at C
between F and 2F
a. real
b. enlarged
c. inverted
d. beyond 2f
between F and C
a. real
b. enlarged
c. inverted
d. beyond C
@F
@F
NO IMAGE
in front of F
9.
Image Description
a.
virtual
b.
enlarged
c.
upright
d.
same side of lens
as the object
NO IMAGE
in front of F
a.
virtual
b.
enlarged
c.
upright
d.
opposite side of
mirror as the object
An object is placed 22 cm from a diverging lens. If a virtual image appears 6 cm from the lens on the same side as the
object, what is the focal length of the lens?
Given:
di = -6 cm (virtual images have negative distances) Find: f (diverging lens means f will be negative)
do = 22 cm
1 1
1
= +
𝑓 𝑑
𝑑
1
1
1
8
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
=
+
= −0.1212
𝑓 −6 22
1
𝑓=
= −0.1212 = −8.25
𝑓
f = -8.25cm
10.
If a virtual image is formed 13 cm along the principal axis from a convex mirror with a focal length of -25 cm, what is
the object’s distance from the mirror?
Given:
di = -13 cm (virtual images have negative distances) Find: do
f = -25 cm (diverging lens means f is negative)
1 1
1
𝑑
do = 27.08 cm
11.
A light ray goes from water (n = 1.33) to crown glass (n = 1.52) at an angle of 37 degrees.
a) Draw and label a picture including the boundary, normal, incident ray, and refracted ray.
water
glass
b) Describe, using WORDS, what is occurring in the picture you drew in part a) above.
The light ray in the water, hits the surface of the glass and because glass has a higher index of refraction, the ray
travels through it, but bends closer to the normal. (The normal is an imaginary line we use as a reference point to
measure angles of incidence and angles of reflection.)
c) Use Snell’s Law to calculate the angle of refraction.
Given: ni = 1.33
nr = 1.52
Θi = 37
𝑛 sin 𝛩 = 𝑛 sin 𝛩
1.33 sin 37 = 1.52 sin 𝛩
1.
sin 𝛩 = = 0.5265
𝛩 = sin
Find: Θr
0.5265 = 31.775
Θ = 31.8°
9
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
12.
Describe the conditions necessary for total internal reflection to occur.
1. Must be going from a higher index of refraction to a lower index of refraction (from high n to low
n)
2. Must be at an angle of incidence higher than the critical angle
13.
Define index of refraction (as a ratio) in equation form.
𝑐
𝑛=
𝑣
10
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
Unit 11: Electricity Essential
questions:
x What are current, potential difference, resistance, and power?
Current: flow of charge carriers (I)
Potential difference: a difference in electric potential between two points (ΔV)
Resistance: opposition to current that is present in the material it is trying to flow through (R)
Power: rate of energy dissipationv(P) x
What do the circuit schematics look like?
They are drawings of all the elements in a circuit.
x
How do you calculate the equivalent resistance and total current in a series
circuit? o Equivalent resistance:
 𝑅 = 𝑅 + 𝑅 + ⋯ (resistance adds up)
How do you calculate the current in each resistor in a series circuit? 
𝐼=𝐼
=𝐼
= ⋯ (current is the same in each part as the
total)
o How do you calculate the potential difference across each resistor in a
series circuit?

𝑉 = 𝐼𝑅, but 𝑉 = 𝑉 + 𝑉 + ⋯ (voltage drops in each part add up to the total voltage)
How do you calculate the equivalent resistance and total current in a parallel
circuit? o Equivalent resistance:
o
x

=
+
+ ⋯ (the inverses of the resistances add up)
o
x
How do you calculate the current in each resistor in a parallel circuit?
 𝐼=𝐼+𝐼
+ ⋯ (current in each part adds up to the total)
o How do you calculate the potential difference across each resistor in a parallel circuit?
 𝑉=𝑉=𝑉
= ⋯(voltage is the same in each part as the total)
How do you calculate the equivalent resistance, total current, current in each resistor, and potential difference across each
resistor in a complex circuit?
First reduce down to either all parallel or all series. Then apply the rules for whichever applies and carry back your results to
Resistance - opposition to current that is present in the
material it is trying to flow through (R)
Conductor – materials where resistance is low (think: metals)
Insulator – materials where resistance is high (think: rubber)
each previous step until you are back at the original complex circuit.
x How do you calculate the power dissipated by a given electrical device?
𝑃 = 𝐼𝑉 𝑜𝑟 𝑃 = 𝐼 𝑅 Key
vocabulary:
Electric field – a region where electric force on a test charge
can be detected (E = F/q)
Current – electric charge per unit of time (I = Q/t)
Practice:
1. In the figure shown at right, calculate the… [Note: The 40.0Ω should be 40.0V] a.
Equivalent resistance
Step 1: 8+2 = 10Ω
Step 2:
=
𝑅 = (. 2)
+
= .2
= 5𝛺
Step 3: 5 + 5 = 10Ω = Req
b.
Total current
Vt = ItReq (rearranged…) It = Vt/Req
It= 40/10 = 4A
c.
Current through each resistor
11
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
In series, total current is the same as the current through each piece, so the 5Ω resistor has 4A. Also, the entire
reduced green box gets 4A…but not each resistor there…the whole thing. So now…consider that inside that green
box you have two branches, each with 10Ω of resistance. Because the two parallel branches are equal, each gets
half the current. So…the 10Ω resistor gets 2A of current. That leaves the red box. There, the two resistors are in
series, so they get the same as the total through the branch, which is 2A.
d.
Voltage through each resistor
Now, just apply V = IR to each resistor since you know
the I and the R in each one to calculate V. Check your
work in the chart below.
Voltage (V)
16
4
20
20
Current (I)
2
2
2
4
Resistance (R)
8
2
10
5
40
4
10
Total
2.
Four resistors with values of 1.0 Ω, 2.0Ω, 3Ω, and 4Ω are connected …in series. What is the equivalent resistance of this
combination?
1+2+3+4 = 10Ω
… in parallel. What is their equivalent resistance?
=
+
+ +
𝑅 = (2.083)
3.
4.
5.
= 2.083
= 0.48Ω
In general, as you connect more resistors
…in series what happens to the equivalent resistance of the comibination?
increases
…in parallel what happens to the equivalent resistance of the comibination? decreases
Unlike charges attract
; like charges
repel
.
An electric hair dryer requires 1500 W at 110 V. What is the resistance of the heating coil in the hair dryer?
Given: P = 1500W
Find: R
V = 110V
𝑃 = 𝐼𝑉
and
𝑉 = 𝐼𝑅 First,
use 𝑃 = 𝐼𝑉 to find current.
1500 = 𝐼(110)
𝐼=
= 13.636
Next, use 𝑉 = 𝐼𝑅to find R.
110 = (13636)𝑅
𝑅=
6.
7.
= 8.067
R = 8.07Ω
A small handheld flashlight has 2 – 1.5 V (AA size) batteries. This gives a potential difference of 3 V across it. The bulb has
a resistance of 5.0Ω. How much current is in the bulb filament?
Given: V = 3V
Find: I
R = 5Ω
𝑉 = 𝐼𝑅
3 = 𝐼(5)
𝐼 = = 0.6
I = 0.6A
An electric field of 4000 N/C is produced by a charge of 7 x 10 -9 C. How far away is the charge?
Given: E = 4000N/C
q = 7 x 10-9C
Find: r
12
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
k = 8.99 x 109 N∙m2/C2 (remember that this is a constant)
𝑘𝑞
𝐸=
𝑟
(8.99 x 10 )(7𝑥10 )
4000 =
=
𝑟
𝑟 =
8.
62.93
𝑟
= 0.0157
r = 0.125m
What is the relationship between current, charge and time? Current equals charge over time
𝐼=
Current and time are
inversely related; current and charged are directly related.
If you hold charge constant and increase the time, what happens to the current?
9.
The bottom of the fraction gets bigger…current decreases.
If you hold charge constant and decrease the time, what happens to the current?
The bottom of the fraction gets smaller…current increases.
When a positive charge moves in the direction of the electric field, what happens to the electrical potential energy associated
with the charge?
The PEe decreases (the charge is moving in the direction it wants to move naturally…so it ‘loses’ PE)
When a positive charge moves in the direction away from the electric field, what happens to the electrical potential
energy associated with the charge? The PEe increases
When a negative charge moves in the direction of the electric field, what happens to the electrical potential energy associated
with the charge?
The PEe increases (the charge is being forced to move in a direction it does not naturally want to move…so it’s ‘gaining’
PE) When a negative charge moves in the direction away from the electric field, what happens to the electrical potential
energy associated with the charge? The PEe decreases
10. Two point charges, initially 5 cm apart, experience a force, F. What is the electric force between the charges when they are
moved to each of the distances below?
𝑘𝑞 𝑞
𝐹=
𝑟
a. …10 cm? if r was originally 5cm, and is now 10cm we can replace r with 2r.
𝑘𝑞 𝑞
𝑘𝑞 𝑞
1 𝑘𝑞 𝑞
𝐹=
= =
(2𝑟)
4𝑟
4 𝑟
b.
So, the new force is 𝐹
…15 cm? if r was originally 5cm, and is now 15cm we can replace r with 3r.
𝑘𝑞 𝑞
𝑘𝑞 𝑞
1 𝑘𝑞 𝑞
𝐹=
= =
(3𝑟)
9𝑟
9 𝑟
So, the new force is 𝐹
c.
…2.5 cm? if r was originally 5cm, and is now 2.5cm we can replace r with 𝑟.
𝑘𝑞 𝑞
𝑘𝑞 𝑞
𝑘𝑞 𝑞
𝐹 === 4
( 𝑟)
𝑟
𝑟
13
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
So, the new force is 4𝐹
11. Two point charges having charge values of 5.0μC and -7.0 μC, respectively, are separated by 2.0 cm. What is the electrostatic
force between them?
Given: r = 2cm = 0.02m
Find: F q1 =
5x10-6C
q2 = 7x10-6C
k = 8.99x109 N∙m2/C2 (constant)
𝑘𝑞 𝑞
𝐹=
𝑟
𝐹=
𝐹 = 786.6𝑁; 𝑎𝑡𝑡𝑟𝑎𝑐𝑡𝑖𝑣𝑒 (𝑏𝑒𝑐𝑎𝑢𝑠𝑒 𝑜𝑛𝑒 𝑖𝑠 𝑝𝑜𝑠𝑖𝑡𝑖𝑣𝑒 𝑎𝑛𝑑 𝑜𝑛𝑒 𝑖𝑠 𝑛𝑒𝑔𝑎𝑡𝑖𝑣𝑒)
12. How is the power affected by…
Use this power equation: 𝑃 = 𝐼 𝑅
a.
…doubling the current in a resistor?
𝑃 = (2𝐼) 𝑅 = 4𝐼 𝑅 So…Power goes from P to 4P
b.
…tripling the current in a resistor?
𝑃 = (3𝐼) 𝑅 = 9𝐼 𝑅 So…Power goes from P to 9P
c.
…decreasing the current in a resistor to half its original value?
𝑃 = ( 𝐼) 𝑅 = 𝐼 𝑅 So…Power goes from P to
𝑃
14
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
Unit 12: Magnetism
Essential questions:
x What are the names of the poles of a magnet? North and south. Which magnetic poles attract? North attracts to south. Which
magnetic poles repel? Like poles repel (north-north or south-south)
x
What does the magnetic field look
like: o
Around a bar magnet?
x
x
x
o
Between two like poles?
o
Between two unlike poles?
o
Around a long, straight, current-carrying wire?
o
Around a loop of current-carrying wire?
o
Around the Earth?
What is a magnetic domain made of?
a region composed of a group of atoms whose magnetic fields are aligned in the same direction
What is the direction of the force on a wire carrying a current in a magnetic field? Right hand rule #1: thumb points in
direction of current, fingers wrap in direction of magnetic field.
o What is the size of that force? 𝐹 = 𝐼𝑙𝐵
What is the direction of the force on a charged particle moving in a magnetic field? Right hand rule #2:
1. Fingers in direction of magnetic field 2.
Thumb in direction of velocity of the proton
3. Palm points in direction of force.
15
Physical Science Semester 1 Exam Review
Name__________________________ Date___________ Per___
[NOTE: if it’s an electron either use left hand rule OR reverse the direction of the force] o
What is the size of that force? 𝐹 = 𝑞𝑣𝐵
x
How can a current be produced in a loop of wire and what is the direction of an induced current?
Three ways to produce a current:
Direction of the induced current:
1. Vary the strength of the magnetic field The direction of an induced current is always such 2. Move the circuit into/out
of the field
that its magnetic field opposes the change causing it.
3. Spin/rotate the circuit in the field
x
What is the mathematical relationship between the frequency and wavelength of an electromagnetic wave?
𝑐 = 𝜆𝑓 x What are the seven regions
of the electromagnetic spectrum in order of decreasing wavelength? Radio, microwave, infrared,
visible, ultraviolet, x-ray, gamma ray
x
How is an electromagnetic wave produced?
Oscillating electric and magnetic fields are perpendicular to each other and induce one another. They create the EM wave
that is perpendicular to each of them. Key vocabulary:
Magnetic domain – a region composed of a group of atoms whose magnetic fields are aligned in the same direction
Electromagnetic induction – the process of creating a current in a circuit by changing the magnetic field strength
Magnetic field – a region where a magnetic force can be detected Practice:
1. Explain Lenz’s Law. Draw a picture or describe an example.
The direction of an induced current is always such that its magnetic field opposes the change causing it.
Example: In the picture below, the blue magnetic field lines are from the magnet. As it is lowered into
the loop of wire, there are MORE downward field lines. The current induced in the wire, will create a
magnetic field that opposes the increase in those downward field lines. Meaning that inside the loop of
wire, the induced current will have a magnetic field that points upward. Using right hand rule for wires
(thumb in direction of current, fingers wrap in direction of magnetic field) you will find that the current
must point as indicated in order for its magnetic field to oppose the change causing it.
2.
3.
What is the instantaneous direction of the force on a proton that enters the magnetic field shown at right? The proton enters
from the left and moves toward the right. UP (toward the top of the page) Remember right
hand rule:
1) Fingers in direction of magnetic field 2) Thumb in direction of velocity of the proton 3)
Palm points in direction of force.
[NOTE: if it’s an electron either use left hand rule OR reverse the direction of the
force]
What is the instantaneous direction of the force on an electron that enters the magnetic
field shown at right? The electron enters from the left and moves toward the right. DOWN
(toward the bottom of the page)
What is the instantaneous direction of the force on a proton that enters the magnetic field
shown at right? The proton enters from the top and moves toward the bottom.
to the RIGHT
What is the instantaneous direction of the force on an electron that enters the magnetic
field shown at right? The electron enters from the top and moves toward the bottom. to the
LEFT
Describe all the methods of inducing an emf in a loop of wire.
1. Vary the strength of the magnetic field
2. Move the circuit into/out of the field
3. Spin/rotate the circuit in the field
16
Name__________________________ Date___________ Per___
Physics I Honors Semester 2 Exam Review
4.
Describe the transmission/propagation of electromagnetic waves.
Oscillating electric and magnetic fields are perpendicular to each other and induce one another. They create the EM wave
that is perpendicular to each of them.
5.
An electron moves north at a velocity of 5 x 105m/s and experiences a magnetic force of 6 x 10-12N west. If the magnetic
field points upward, what is the magnitude of the magnetic field?
Given: q = 1.6x10-19C
Find: B (magnetic field)
5
v = 5x10 m/s
F = 6x10-12N west
6𝑥10
𝐹 = 𝑞𝑣𝐵
= (1.6𝑥10
)(5𝑥10 )𝐵
𝐵=
= 75
B = 75 Teslas
6.
If a wire carries a current of 6A and a magnetic field of 0.004T produces a 5 x 10-3N force on it, how long is the wire?
Given: I = 6A
Find: l (length)
B = 0.004T
F = 5x10-3N
5𝑥10
𝐹 = 𝐼𝑙𝐵
= (6)𝑙(0.004)
𝑙=
= 0.208
l = 0.208m (which is 20.8cm)
7.
A coil with 300 turns of wire has an area of 0.4m2. In 0.4 s it turns through 90°. If the average induced emf is 50V, what is
the strength of the magnetic field?
Given: N = 300 turns
Find: B (magnetic field)
A = 0.4m2
Δt = 0.4s
emf = 50V
𝑁𝛥𝛷
𝑒𝑚𝑓 = −
𝐴𝑁𝐷 𝛷 = 𝐴𝐵
𝛥𝑡
In order to find B, we need to first find Φ
(300)𝛷
50 = −
0.4
𝛷=−
= 0.0667
𝛷 = 𝐴𝐵
0.0667 = (0.4)𝐵
0.
𝐵 = = 0.16675
B = .167T
17
Name__________________________ Date___________ Per___
Physics I Honors Semester 2 Exam Review
Unit 13: Modern
Essential questions:
x What phenomena’s could not be explained by the wave model of light and how do they demonstrate the particle-like nature
of light? Photoelectric Effect and Compton Effect
x What evidence is there for the wave-like nature of matter?
de Broglie’s evidence
x How did the early models of the atom lead to the Quantum Model? x What led to the current nuclear
model and explain how energy produced in nuclear reaction? x
What are the three families of elementary
particles and how are the electron, proton, and neutron classified?
x What are the four fundamental interactions/forces in nature?
Strong nuclear – strongest, holds nuclei together
Weak nuclear – responsible for beta decay
Electromagnetic
Gravitational – weakest, holds the universe together Key
vocabulary:
de Broglie waves –matter waves; evidence of the wave like
nature of matter
Photoelectric effect – when electrons are ejected from a
material when light of a certain frequency is shined on the
surface of the metal
Quantum Model – model dealing with the physical
phenomena where action in the atom is on the order of
Planck’s constant (really small stuff!)
Fusion – small nuclei are fused/combined together and there
is a lot of energy expelled.
Fission – larger nuclei are split and there is a lot of energy
expelled, but also there is nuclear waste.
Practice:
1. The de Broglie wavelength of an object has what sort of relationship with speed? Inverse! 𝜆
2.
3.
=
According to Einstein, what it the relationship between a particle’s mass and the energy that it could potentially release?
𝐸 = 𝑚𝑐
Photoelectric electric effect is most easily observable for light under what conditions?
The light waves have short wavelengths (but high energy, high frequency), will deliver packets of to the electrons and
cause them to eject from the material’s surface.
4.
5.
6.
7.
The Quantum Model of light is useful for what sort of predictions?
The photons wavelength and the characteristic light emitted help identify the element. This allows us to analyze the
composition of materials. Astronomers and astrophysicists use this heavily to determine the composition of stars.
Describe each of the four fundamental forces of nature.
Strong nuclear – strongest, holds nuclei together
Electromagnetic – responsible for attraction and repulsion of charges
Weak nuclear – responsible for beta decay
Gravitational – weakest, holds the universe together
Describe each of the following types of nuclear decay:
a. Alpha decay – an alpha particle is emitted from a helium nucleus [least powerful penetration]
b. Beta decay – an electron is emitted from a neutron
c. Gamma decay – photons are released (high energy, but no mass) [most powerful penetration]
Compare and contrast fission and fusion.
Fission
Similarities
Fusion
18
Name__________________________ Date___________ Per___
Large nuclei split (usually uranium)
Example: the type of power at a
nuclear power plant
Both involve rearranging/changing the
nucleus of an element Both
release LOTS of energy
Combines smaller nuclei – usually
hydrogen
Example: all the energy the sun has is
released from fusion reactions
19