AP Physics 2- Review for 1st Semester Final
Fluids
Fluid dynamics is the study of substances that flow. Fluids can be either a gas or a liquid.
We examined pressure a fluid exerts on an object and the buoyant force provided by a fluid.
Example: the pressure acting on an object from a fluid is the same at all points on the object.
1. A sheet of paper lies on a table. The paper measures 20.0 cm by 30.0 cm. Calculate the force exerted on
the paper by the atmosphere. Figure that the pressure exerted by the atmosphere is 1.013 x 105 Pa.
F=6078N
2. What is the (a) buoyant force acting on a cube of copper that measures 2.00 cm on its each side if it is
immersed in water and (b) the apparent weight of the cube?
a) Fb= 0.08N
b) F = 0.63N
We also looked at the velocity of moving fluids in relation to the area of the container and at the Bernoulli
principle. You should be able to solve any of those type of problems.
3. Water flows through a garden hose that has a diameter of 2.50 cm at a speed of 5.25 m/s. What is the
speed of the water when it spurts out of a nozzle that has a diameter of 0.120 cm?
V= 2278m/s
4. A liquid with a density of 1.65x103 kg/m3 flows through 2 horizontal sections of tubing joined end to end. In
the first section the cross sectional area is 10.0cm2, the flow speed is 275cm/s, and the pressure is 1.20x10 5
pa. I the second section the cross sectional area is 2.50 cm2. Calculate:
a. the flow speed in the smaller section b) the pressure in the smaller section
a) V=11.0m/s
b) P2= 26414 pa
Thermo
Temperature: Average KE of the particles. Depends on average speed only of particles (atoms or molecules)
A bucket of water at 50o has the same temperature as a cup of water at 50o
Thermal Energy: Average KE and the mass of the particles Depends on speed and the mass of the particles.
A bucket at 50o has more thermal energy than a cup at 100o. Bucket of $50 bills has more money than a
cup of $100’s. While the particles are going faster in the cup, there are so many more in the bucket.
Heat: Transfer of energy between objects that have different temperatures. The direction of heat flow
depends on temperature. From hot objects (more energy) to cold objects (less energy).
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1. A 345 g chunk of gold at 98.5C is dropped into 656 g of H2O at 22.5. (a) What will the final
temperature of the gold be after the system reaches equilibrium? (b) What is the apparent weight of
the gold in the water?
Qgold=1651j, Qwater = 81447j , Qtot=827958j=.656kg(4186) ΔT ΔT=301K or 28.5C
2. 3450 J of energy are required to raise the temperature of a chunk of copper from 23.0C to 315C.
What is the mass of the copper?
M=0.0305kg
Gas Laws
Pressure:
P  F Area Measured in N m2 called a Pascal.Collisions against an object are felt as pressure.
Universal Gas Law: PV  nRT (Static cases)
or
PV
PV
1 1
 2 2 (Changing cases)
n1T1 n2 T2
1. An ideal gas is confined in a box that initially has pressure P. If the absolute temperature of the gas is
doubled and the volume of the box is quadrupled, the pressure is:
P=1/2
Waves and Sound
A wave is a disturbance in a medium. It is a way of transferring energy.
Wavelength λ - the distance from one point on a wave to the same point on the next wave. For example, from
crest to crest or trough to trough. Measured in meters.
Amplitude A – is the height of a crest or trough, measured from the equilibrium point in meters.
Frequency f – is how many wave pass a certain point in each period of time, usually waves/second or hertz.
Period T – is how many seconds for one wave to pass a certain point. The inverse of frequency, measured in
seconds.
Velocity v – the speed of a wave pulse. Depends on the medium through which the wave is traveling. The only way
to change wave speed is to change the medium.
Node-where a standing wave moves the least. (least amplitude). The quietest point on a sound wave.
Antinode-where a standing wave moves most (greatest amplitude). The loudest point on a sound wave.
You should be able to identify wave patterns by counting nodes and antinodes on a standing wave.
1.A standing wave of frequency 5 hertz is set up on a string 2 meters long with nodes at both ends and in the
center, as shown at right.
2. The speed at which waves propagate on the string is
a. 0.4 m/s
b. 2.5 m/s
c. 5 m/s
d. 10 m/s
m/s
e. 20
3. The fundamental frequency of vibration of the string is
b. 2.5 Hz
c. 5hz
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c. 5 Hz
d. 7.5 Hz
B
20.
Which graph above represents a higher Frequency?
a. Graph A
b. Graph B
c. They are the same
21. Which graph above represents a higher Wavelength?
a. Graph A
b. Graph B
c. They are the same
22. Which graph above represents a louder sound?
a. Graph A
b. Graph B
c. They are the same
Interference
Diffraction is the bending of a wave around a barrier or through an opening. If we pass a light wave
through a narrow single slit, it will behave very similarly to water waves, with the edges of the light
waves lagging behind the center of the waves. If we place a screen opposite to the single-slit opening,
we would see a bright light near the center of the screen with smaller bright spots on either side. The bright
spots indicate constructive interference and the dark spots are destructive.
Use Young’s equation to solve for λ, d, L, or order.
or
Q Two sources, S1 and S2, are producing 2.0 cm wavelength waves. Destructive interference occurs at point
P, which happens to be on the second destructive line past the center (zero order) line. The distance from S1
to P is 26 cm. What is the distance between S2 and P? Draw a sketch of the situation.
Refraction
Light can be refracted, or bent, when it passes from a medium of one density into another medium. The
speed of light changes in a medium according to the index of refraction, n, for that medium.
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, where c is the speed of light and v is the velocity in the medium. The angle of refraction,
from the normal, follows Snell’s law
. You should be able to sketch or identify a ray
diagram, and calculate the angle of incident or refraction for a ray passing from one medium to another.
1. The critical angle for the liquid/air interface is 48°. What path does
light ray X take?
E
2. The ray is passing from water, n=1.33, into an unknown substance. The
incident ray is at 50˚ from the normal and the refracted is 60 ˚ Calculate n for the unknown substance.
What is the speed of light in this material?
N=1.18
Geometric optics: reflection in plane & curved mirrors- lenses
You should be able to sketch (or identify) a ray diagram for the image produced by plane mirror, curved
mirror or lens, and describe the characteristics of the images. For example, upright, virtual, enlarged. You should
also be able to distinguish between concave and convex mirrors; converging and diverging lenses. Use the lens
formula to determine do, di, or f given the the other two.
Use do & di to determine image size and magnification.
3. A converging (convex) lens has a focal length of 15.0 cm. A 5.0-cm tall candle is placed
at a distance of 40.0 cm to the left of the lens. Sketch the ray diagram and calculate the image distance and size.
Od=40cm
C=30cm
f
f
15cm
Id = 24cm I= 3.0cm
A
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23. A 5 μC charge exerts a 20 N force on a 10 μC charge. The magnitude of the force the 10 μC charge exerts on
the 5 μC charge is:
a. 5 N
b. 10 N
c. 20 N
d. 40 N
24. Two charge particles are separated by a distance r. If the distance between them is now doubled (2r) the new
electrical force between them would be:
a. 4x greater
b. 2x greater
c. the same d. ½ as great e. ¼ as great
AP Equation Sheet
X = VT + Xo
Vf = aT + Vo
ΔX = ½ aT2 + VoT
Vf2 = 2a ΔX + Vo2
ω= θ/T
ΣF = 0
Fg = gm
Fg =
+ Xo
V = rω
ΣF = ma
F k = μFn
s = rθ
τ = Frsinθ
F =KX + F
V = fλ
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