Radiant energy from the Sun arrives at Earth with an intensity of $1.5 kW/m^2.$ Making the rough approxima- Sion that all photons are absorbed, find (a) the radiation pressure and (b) the total force experienced by Earth due to this “solar wind.”

Scientists think that Earth once had naturally existing plutonium-$239$. Suppose Earth had $10$ trillion tons of $\mathrm{Pu}-239$ when it formed. Given plutonium's half-life of $24,000$ years and Earth's current age of $4.6$ billion years, how much would remain today? Use your answer to explain why plutonium is not found naturally on Earth today.

The average distance between the earth and the sun is approximately $1.495 \times 10^{11} \mathrm{~m}$

Estimate the average speed at which the earth rotates around the sun in $\mathrm{km} / \mathrm{s}$. Use $365.25$ days per year.

The average distance between the earth and the sun is approximately $1.495 \times 10^{11} \mathrm{~m}$

Estimate the distance in kilometers that the earth travels around the sun in one year. Write your answer in scientific notation. Round to the nearest hundredth.

In the troposphere, what is the relationship between air temperature and the height above Earth?

A solar eclipse occurs when the Moon passes between the Earth and the Sun. Use a diagram to show why some areas of the Earth see a total eclipse, other areas see a partial eclipse, and most areas see no eclipse

The frequency of light reaching Earth from a particular galaxy is $15 \%$ lower than the frequency the light had when it was emitted. Is this galaxy moving toward or away from Earth? Explain. Give your answer as a fraction of the speed of light.

Suppose that a star forms an angle $\theta$ with respect to Earth and the sun. Let the coordinates of Earth be $(x, y)$, those of the star $(0,0)$, and those of the sun $(x, 0)$. Find an equation for $x$, the distance between the sun and the star, as follows.

Solve your equation for $x$.

An electromagnet consists of 200 loops and has a length of $10.0 \mathrm{~cm}$ and a cross-sectional area of $5.00 \mathrm{~cm}^2$. Find the resonant frequency of this electromagnet when it is attached to the Earth (treat the Earth as a spherical capacitor).

Use the following values, where needed: radius of the Earth = 4000 mi = 6440 km, 1 year (Earth year) = 365 days (Earth days), 1 AU =

$$92.9 \times 10 ^ { 6 }$$

mi=

$$150 \times 10 ^ { 6 } \mathrm { km }$$

. The dwarf planet Pluto has eccentricity e = 0.249 and semimajor axis a = 39.5 AU. Find the perihelion and aphelion distances.

Apply The average speed of the coronal solar wind is $450 \mathrm{~km} / \mathrm{s}$. How long does it take a particle in such a wind to reach Earth? (Assume that the distance from Earth to the sun is $150,000,000 \mathrm{~km}$.)

What is the oxidation number of alkaline earth metals in their compounds? Of alkali metals?

If a star that is 20 light-years from Earth explodes, gravitational waves from the explosion would reach Earth in (a) less than 20 years. (b) 20 years. (c) more than 20 years. (d) None of these.

The temperature at the surface of the Sun is approximately $5700 \mathrm{~K}$, and the temperature at the surface of the Earth is approximately $290 \mathrm{~K}$. What entropy change occurs when $1000 \mathrm{~J}$ of energy is transferred by radiation from the Sun to the Earth?