AST 110 - SmartWork Chapter 4

The "second" high tide is caused by A. the Sun, which always pulls in the opposite direction from the Moon. B. stronger gravity pulling on Earth on the side opposite the Moon. C. weaker gravity pulling on Earth on the side opposite the Moon. D. the Sun canceling out some of the Moon's gravity, no matter which way it pulls.

C. weaker gravity pulling on Earth on the side opposite the Moon.

Astronauts in a space shuttle can float while orbiting Earth. Why are these astronauts weightless? A. They and the space shuttle have escaped from Earth's gravity. B. They are falling around Earth at the same rate as the shuttle. C. They are affected equally by the Moon's gravity and Earth's gravity. D. Everything in the orbiting shuttle is shielded from Earth's gravity.

B. They are falling around Earth at the same rate as the shuttle.

For a pair of objects, the center of mass is located A. along the line between the two objects, closer to the less massive object. B. along the line between the two objects, closer to the more massive object. C. at the center of the more massive object. D. at the center of the less massive object.

B. along the line between the two objects, closer to the more massive object.

As two objects orbit one another, they are always A. on opposite sides of the center of mass, traveling in opposite directions in space. B. on opposite sides of the center of mass, traveling in the same direction in space. C. on the same side of the center of mass, traveling in the same direction in space. D. on the same side of the center of mass, traveling in opposite directions in space.

A. on opposite sides of the center of mass, traveling in opposite directions in space.

To begin exploring the simulation, set parameters for "Mercury" in the "Choose Planet" panel and then click "ok." Click the "Newtonian Features" tab at the bottom of the control panel. Select "Show Solar System Orbits" and "Show Grid" under Visualization Options. Drag the Animation Rate Slider almost all the way to the left, and press the "Play" button. Examine the graph at the bottom of the panel. In the Newtonian Features graph, mark the boxes for "Vector" and "Line" that correspond to the acceleration. These will insert an arrow that shows the direction of the acceleration, and a line that extends the arrow. Think about Newton's second law. In what direction is the force on the planet? A. toward the Sun B. toward Mercury C. 90 degrees offset from the direction of the velocity D. away from the Sun

A. toward the Sun

If the Moon had twice the mass that it does, how would the strength of the lunar tides change? A. The highs would be lower, and the lows would be higher. B. Both the highs and the lows would be higher. C. The highs would be higher and the lows would be lower. D. Nothing would change.

C. The highs would be higher and the lows would be lower.

If we wanted to increase the Hubble Space Telescope's altitude above Earth and keep it in a stable orbit, we also would need to A. increase its weight. B. decrease its weight. C. increase its orbital speed. D. decrease its orbital speed.

C. increase its orbital speed

If you went to Mars, your weight would be A. higher because you are closer to the center of the planet. B. the same as on Earth. C. lower because Mars has lower mass and a smaller radius that together produce a lower gravitational force. D. lower because Mars has two small moons instead of one big moon, so there's less tidal force.

C. lower because Mars has lower mass and a smaller radius that together produce a lower gravitational force. Both the planet's mass and your distance from the center of the planet affect the gravitational force and therefore your weight. If Mars had the same mass as Earth, its smaller radius would mean that it was denser and you would weigh more there. However, the mass of Mars is lower than that of Earth, and you would actually weigh less on the Red Planet.

The connection between gravity and orbits enables astronomers to measure the __________ of stars and planets. A. distances B. compositions C. masses D. sizes

C. masses

If an object crosses from farther to closer than the Roche limit, it A. begins to accelerate very quickly. B. can no longer be seen. C. slows down. D. may be torn apart.

D. may be torn apart.

Compared to your mass on Earth, on the Moon your mass would be A. lower because the Moon is smaller than Earth. B. lower because the Moon has less mass than Earth. C. higher because of the combination of the Moon's mass and size. D. the same; mass doesn't change.

D. the same; mass doesn't change.