A spaceship leaves Earth traveling at $0.65 c$. A second spaceship leaves the first at a speed of $0.82 c$ with respect to the first. Calculate the speed of the second ship with respect to Earth if it is fired in the same direction the first spaceship is already moving.

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.

The speed of light is about $1.9 \times 10^{5}$ miles per second. It takes about 500 seconds for light to travel from the sun to Earth. What is the approximate distance between Earth and the sun? Write in scientific notation.

The orbital revolution of the Moon about Earth takes about 27.3 days and is in the same direction as Earth's rotation (24 h). Use this information to show that high tides occur everywhere on Earth every 12 h and 26 min.

Write down logical representations for the following sentences, suitable for use with Generalized Modus Ponens:

• a. Horses, cows, and pigs are mammals.
• b. An offspring of a horse is a horse.
• c. Bluebeard is a horse.
• d. Bluebeard is Charlie’s parent.
• e. Offspring and parent are inverse relations.
• f. Every mammal has a parent.

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.”

One kg weighs $10$ N on Earth. Would it weigh more or less on the Moon?

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.

Light from the Sun takes approximately $8.3 \mathrm{~min}$ to reach the Earth. During this time interval the Earth has continued to rotate on its axis. How far is the actual direction of the Sun from its image in the sky?

Understanding Relationships How can it be that Earth is at perihelion during wintertime in the Northern Hemisphere?

Compare the fuel required for a trip from Earth to Moon with that required for the return trip.

John's mass is $65.0 \mathrm{~kg}$ on the earth. Express his U.S. (a) mass and (b) weight $40 \overline{0} 0\ \mathrm{mi}$ above the surface of the earth, where $g=7.85 \mathrm{ft} / \mathrm{s}^2$ ?

The heterotroph hypothesis is an attempt to explain (1) how Earth was originally formed (2) why simple organisms usually evolve into complex organisms (3) why evolution occurs very slowly (4) how life originated on Earth

The rotation of the earth on its axis causes objects sitting on the equator to have a radial acceleration toward the center of the earth. How short would the earth's day (in hours) have to be in order for the radial acceleration at the equator to be equal to g?