The gravitational attraction of the Sun and the Moon on the Earth produces tides. The Sun’s tidal effect is about half as great as the Moon’s. The direct pull of the Sun on the Earth, however, is about $175$ times that of the Moon. Why is it then that the Moon causes the larger tides?

What is the definition of an astronomical unit? A. the average distance from Jupiter to the Sun B. the average distance from Earth to the Moon C. the average distance from Earth to the Sun D. the average distance from the Sun to the next nearest star.

Choose the best answer for each question. Which of the following is true about an object in free fall? A) Its acceleration depends on its mass. B) It has no inertia. C) It pulls on Earth, and Earth pulls on it. D) Its momentum is constant.

When observed from the sun at a particular instant, Earth and Mars appear to move in opposite directions with speeds 108,000 km/h and 86,871 km/h, respectively. What is the speed of Mars at this instant when observed from Earth?

A spaceship travels toward Earth at a speed of 0.97c. The occupants of the ship are standing with their torsos parallel to the direction of travel. According to Earth observers, they are about 0.50 m tall and 0.50 m wide. What are the occupants' (a) height and (b) width according to others on the spaceship?

The atoms that make up the Earth and the Moon contain enormous amounts of charge as well as mass. The Earth and Moon exert strong gravitational forces on each other, and yet they exert no electrical force on each other. Explain how this is possible.

The mass of the sun is approximately

$$2 X 10^{30}$$

kilograms, and the mass of Earth is approximately

$$6 X 10^{24}$$

kilograms. How many times greater is the mass of the sun than the mass of Earth? Write your answer in decimal notation.

Solve. Write the answer in scientific notation.

The mass of Earth is $5.9 \times 10^{24} \mathrm{~kg}$. The mass of the sun is $2 \times 10^{30} \mathrm{~kg}$. How many times heavier is the sun than Earth?

The earth is at the origin, the moon is at the point $(384, 0)$, and a spaceship is at $(280, 90)$, where distance is in thousands of kilometers.

(c ) The gravitational force on the spaceship from the earth is $461$ newtons and from the moon is $26$ newtons. What is the resulting force?

The energy from solar radiation falling on Earth is

$$1.07 \times 10 ^ { 16 } \mathrm { kJ } / \mathrm { min }$$

How much loss of mass from the Sun occurs in one day from just the energy falling on Earth?

A space traveler whose mass is $75.0$ kg leaves Earth. Com- pute his weight $(a)$ on Earth, $(b)$ on Mars, where $g=3.72$ m/s$^2$, and $(c)$ in interplanetary space. $(d)$ What is his mass at each of these locations?

Assume that the rate of change of the human population of the earth is proportional to the number of people on earth at any time, and suppose that this population is increasing at the rate of 2% per year. The 1979 World Almanac gives the 1978 world population estimate as 4219 million; assume this figure is in fact correct. (a) Using this data, express the human population of the earth as a function of time. (b) According to the formula of part (a), what was the population of the earth in 1950? The 1979 World Almanac gives the 1950 world population estimate as 2510 million. Assuming this estimate is very nearly correct, comment on the accuracy of the formula of part (a) in checking such past populations. (c) According to the formula of part (a), what will be the population of the earth in 2000? Does this seem reasonable? (d) According to the formula of part (a), what was the population of the earth in 1900? The 1970 World Almanac gives the 1900 world population estimate as 1600 million. Assuming this estimate is very nearly correct, comment on the accuracy of the formula of part (a) in checking such past populations. (e) According to the formula of part (a), what will be the population of the earth in 2100? Does this seem reasonable?

Describe how the Moon and the Sun cause tides on Earth.

Consider the reasons and evidence that the AMA gives to support the view that animal research is necessary for medical science. Does the AMA provide sufficient support for its claim? Explain your opinion.