In your own words:

Paragraph #1: Define an observational study.

Paragraph #2: Explain the main types of observational studies.

Paragraph #3: Discuss the advantages and disadvantages of these observational studies.
Paragraph #4: Give examples of which statistics are useful to look at and which statistics are there to mislead people in these observational studies.
Paragraph #5: Summarize how to interpret mainstream research.
Paragraph #6: Explain why people shouldn’t trust observational studies.

The sodium spectrum is dominated by the bright doublet known as the Sodium D-lines at λ1=588.995 and λ2=589.5924 nanometers. Say, you've got a diffraction grating with 3900 grooves/cm. Find the angles corresponding to the maxima of λ1 and λ2 in the first order: ° and ° Find the difference between these angles: °. Now do the same for the second order: °, °, and °. Notice that the resolution increases with the order! In what maximum order can these lines be observed?

True/False

1) A wire carrying current due east in a magnetic field is deflected due north. The magnetic field must have a component that points into the ground

2) The self-inductance of a solenoid depends on the geometry of the solenoid and is independent of the current flowing through it

3) A horizontal bar that is oriented east to west is pulled vertically upward through a magnetic field that points due north. The east end of the bar is at a higher potential than the west end

4) An AC source of fixed rms voltage is connected to an inductor. When the frequency of the source increases, the inductive reactance decreases

5) An AC source of fixed rms voltage is connected to a capacitor. When the frequency of the source decreases, the rms current flowing through the capacitor increases

6) When the amplitude of the electric field of an EM wave traveling in a vacuum is doubled, the intensity is always quadrupled

7) For an EM wave traveling in a vacuum, the energy carried in its electric field is always larger than the energy carried in its magnetic field

8) The image formed from a spherical mirror can be determined from any two rays that originate from the same point on the object

9) The images formed from a convex mirror are always virtual, upright, and larger than the objects that form them

pls report answers in scientific notation and standard units

There exists a flat, smooth interface between a region of fresh water and one of polystyrene. For light that travels through the water and is incident on the interface at an angle of 29.00 ° relative to the interface normal, calculate the angle, relative to the interface normal, at which the light refracts into polystyrene.

State in which medium the speed of the light is greater and calculate by what factor it is larger than in the other.

Does light need to be travelling from water into polystyrene of from polystyrene into water for total internal reflection to be possible at this interface? Answer this question explicitly and calculate the critical angle.

Members of the astronomy club just posted an article about the discovery of a small comet which orbit is in the same orbit plane as the Earth. In the article it is reported that the observation took place when the comet was eclipsed by the sun just passing the aphelion, in a relative distance at that moment of 3.82 UA and an orbit with eccentricity of e=0.777.

They are calling you to form part of the group of immediate reaction to determine if the comet is a rick to planet Earth. Do the calculation. Use Kepler laws to determine if the ellipse of the comet (period, formula, intersection points with the ellipse of the earth).

When the transportation of natural gas in a pipeline is not feasible for economic
reasons, it is first liquefied using nonconventional refrigeration techniques and
then transported in super-insulated tanks. In a natural gas liquefaction plant,
the liquefied natural gas (LNG) enters a cryogenic turbine at 3 MPa and -160
°C at a rate of 20 kg/s and leaves at 0.3 MPa. If 115 kW power is produced by
the turbine, determine the efficiency of the turbine. Take the density of LNG to
be 423.8 kg/m3

A beam of light containing red (660 nm) and violet (410 nm) wavelengths travels from air, through a flat piece of crown glass 1.92 cm thick, and then back to air. (a) If the beam has an angle of incidence of 36.0° in air, determine the angle at which the two colors of light emerge from the crown glass. The index of refraction respectively for red and violet light in crown glass is 1.512 and 1.530. (Enter a number to three decimal places.)

red angle:

Violet angle:

(b) Determine the distance separating the red and violet light as it emerges from the glass. (in cm)

A company owns and operates an electric sign that uses 300 individual lamps to display messages. The sign currently uses bulbs that cost $2.50 each and last for an average of 2 years. These lamps draw 60 watts of power each. The company is considering switching to LED bulbs that have an estimated life span of 10 years and cost $30 each. The LED bulbs only draw 7.5 watts of power for the same light levels. Replacing the lamps requires special equipment and labor that will cost $1,200 dollars. This work is performed every two years for the current lamps and at the end of 10 years for the LED lamp. The sign operates 2500 hours each year. Electricity costs $0.075/kWh. The company uses 7% as its rate of return. Assume that the maintenance protocol replaces all 300 lamps when the average lifetime is reached. Consider costs to be negative numbers and benefits as positive a.) Compute the total annual cost of operating the sign using the 300, 60 watt lamps. DO NOT include dollar signs the answer. b.) Compute the total annual cost of operating the sign using the 300, 7.5 watt LED lamps. DO NOT include a dollar sign in the answer. (Note: this is a cost and should be a negative value c.) Determine the present worth of benefits by subtracting the expenses of owning and operating the LED bulbs from the conventional bulbs. (Hint: comparing the alternatives requires equal life spans. Use least common multiple of lives) d.) Compute the benefit-cost ratio

Occasionally, huge icebergs are found floating on the ocean's currents. Suppose one such iceberg is 124 km long, 41.5 km wide, and 217 m thick.

(a) How much heat in joules would be required to melt this iceberg (assumed to be at 0°C) into liquid water at 0°C? The density of ice is 917 kg/m³ and the latent heat of fusion is 334 kJ/kg.

(b) The annual energy consumption for Australia in the 2017-2018 financial year was 6.172×10¹⁸ J. If this energy was delivered to the iceberg every year, how many years would it take before the ice melted?

On a cloudless day, the sunlight that reaches the surface of the Earth has an intensity of about 1.01×10³ W/m². What is the electromagnetic energy contained in 4.3 m³ of space just above the Earth's surface?

c = 3.00×10⁸ m/s

what's πt of van der waals gas? and how to solve this

In a common demonstration an instructor "races" various round objects by releasing them from rest at the top of an inclined plane and letting them roll down the plane. Before the objects are released the students guess which object will win.

A) Find the ratio of the final speeds for a solid sphere and a solid cylinder.

B) Assuming that the masses of the two cylinders are the same, what is the ratio of the rotational kinetic energy of the solid sphere to the solid cylinder at the bottom of the ramp?

SET UP We use conservation of energy, ignoring rolling friction and air drag. If the objects roll without slipping, then no work is done by friction and the total energy is conserved. Each object starts from rest at the top of an incline with height hh, so Ki=0Ki=0, Ui=mghUi=mgh, and Uf=0Uf=0 for each. The final kinetic energy is a combination of translational and rotational energies:

Kf=12mvcm2+12Icmω2Kf=12mvcm2+12Icmω2

Both vcmvcm and ωω are unknown, but if we assume that the objects roll without slipping, these two quantities are proportional. When an object with radius RR has rotated through one complete revolution (2ππ radians), it has rolled a distance equal to its circumference (2πR)(2πR). Thus the distance traveled during any time interval ΔtΔt is RR times the angular displacement during that interval, and it follows that vcm=Rωvcm=Rω.

SOLVE For the cylindrical shell, Ishell=MR2Ishell=MR2. Conservation of energy then results in

0+Mghvcm====12Mvcm2+12Icmω212Mvcm2+12(MR2)(vcm/R)212Mvcm2+12Mvcm2=Mvcm2gh−−√0+Mgh=12Mvcm2+12Icmω2=12Mvcm2+12(MR2)(vcm/R)2=12Mvcm2+12Mvcm2=Mvcm2vcm=gh

For the solid cylinder, Isolid=12MR2Isolid=12MR2 and the corresponding equations are:

0+Mghvcm====12Mvcm2+12Icmω212Mvcm2+12(12MR2)(vcm/R)212Mvcm2+14Mvcm2=34Mvcm243gh−−−√0+Mgh=12Mvcm2+12Icmω2=12Mvcm2+12(12MR2)(vcm/R)2=12Mvcm2+14Mvcm2=34Mvcm2vcm=43gh

We see that the solid cylinder's speed at the bottom of the hill is greater than that of the hollow cylinder by a factor of 43−−√43.

We can generalize this result in an elegant way. We note that the moments of inertia of round objects about axes through their centers of mass can be expressed as Icm=βMR2Icm=βMR2, where ββ is a pure number between 0 and 1 that depends on the shape of the body. For a thin-walled hollow cylinder, β=1β=1; for a solid cylinder, β=12β=12; and so on. From conservation of energy,

0+Mghvcm====12Mvcm2+12Icmω212Mvcm2+12(βMR2)(vcm/R)212(1+β)Mvcm22gh1+β−−−√0+Mgh=12Mvcm2+12Icmω2=12Mvcm2+12(βMR2)(vcm/R)2=12(1+β)Mvcm2vcm=2gh1+β

REFLECT This is a fairly amazing result; the final speed of the center of mass doesn't depend on either the mass MM of the body or its radius RR. All uniform solid cylinders have the same speed at the bottom, even if their masses and radii are different, because they have the same ββ. All solid spheres have the same speed, and so on. The smaller the value of ββ, the faster the body is moving at the bottom (and at any point on the way down). Small-ββ bodies always beat large-ββ bodies because they have less kinetic energy tied up in rotation and have more available for translation. For the hollow cylinder (β=1β=1), the translational and rotational energies at any point are equal, but for the solid cylinder (β=12)(β=12), the rotational energy at any point is half the translational energy. Considering the values of ββ for round objects for an axis through the center of mass, we see that the order of finish is as follows: any solid sphere, any solid cylinder, any thin spherical shell, and any thin cylindrical shell.

1. Why is two interleaved books so hard to separate?
Explain this fermi problem with an FBD and derived formulas.

A student stands at the edge of a cliff and throws a stone horizontally over the edge with a speed of vi = 10.0 m/s. The cliff is h = 41.9 m above a body of water as shown in the figure below. With what speed and angle of impact does the stone land?