Question

hmh science dimensions earth science, unit 4, lesson 2, pages 197 - 198

1. explain keplers second law of planetary motion. how does a planets distance from the sun affect its orbital velocity?
2. what are the perigee and apogee of orbits?
3. based on keplers laws, how do the orbital speeds of distant planets compare to those of planets closer to the sun? use neptune and mercury as examples in your explanation.

hmh science dimensions earth science, unit 4, lesson 2, pages 199 - 201

1. what is gravity, and how does it affect the movement of objects in space?
2. how does the mass of an object influence its gravitational pull? provide an example from the text.
3. describe how the orbits of planets are affected by changes in speed and distance.

Explanation:

1. Kepler's second law states that a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. When a planet is closer to the Sun (smaller distance), it must move faster (higher orbital velocity) to sweep out the same - area in the same time as when it is farther away.
2. The perigee is the point in an object's orbit around a celestial body where it is closest to that body. The apogee is the point in the orbit where the object is farthest from the celestial body.
3. According to Kepler's laws, planets closer to the Sun have higher orbital speeds. Mercury, being the closest planet to the Sun, has a much higher orbital speed than Neptune, which is a distant planet. This is because the gravitational pull of the Sun is stronger on closer - planets, causing them to move faster in their orbits.
4. Gravity is a force of attraction between two masses. In space, it causes objects to move in curved paths, such as planets orbiting the Sun. It also affects the motion of satellites around planets.
5. The gravitational pull of an object is directly proportional to its mass. For example, the Sun has a much larger mass than the Earth, so its gravitational pull is much stronger, keeping the planets in their orbits.
6. An increase in a planet's speed while at a certain distance from the Sun can cause it to move to a higher - energy orbit (larger semi - major axis). A decrease in speed can cause it to move to a lower - energy orbit. Changes in distance also affect the orbital speed according to Kepler's laws. If a planet moves closer to the Sun, its speed increases, and if it moves farther away, its speed decreases.

Answer:

1. Kepler's second law: A line joining a planet and the Sun sweeps out equal areas in equal times. Closer to the Sun, higher orbital velocity.
2. Perigee: Closest point in orbit. Apogee: Farthest point in orbit.
3. Planets closer to the Sun have higher orbital speeds. E.g., Mercury is faster than Neptune.
4. Gravity is a force of attraction. In space, it curves object paths.
5. Gravitational pull is proportional to mass. E.g., Sun's strong pull due to large mass.
6. Speed changes can alter orbit energy. Distance changes affect speed (closer - faster, farther - slower).