6.1.2 The Solar System (3)
Resources |
Revision Questions |
Physics
Login to see all questions
Click on a question to view the answer
1.
Describe how the Sun's mass influences the orbital speed of planets. Explain why planets closer to the Sun have different orbital speeds compared to those further away.
The Sun's mass directly influences the orbital speed of planets through the relationship between gravitational force and centripetal force. For a planet to maintain a stable orbit, the gravitational force pulling it towards the Sun must be balanced by the centripetal force required to keep it moving in a circular path. This centripetal force is provided by the planet's velocity.
Planets closer to the Sun have higher orbital speeds. This is because they experience a stronger gravitational pull from the Sun. To counteract this stronger pull and maintain a stable orbit, they need to move faster. The further a planet is from the Sun, the weaker the gravitational pull. Therefore, they can orbit at slower speeds without being pulled into the Sun.
This relationship is described by Kepler's Third Law, which states that the square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit. This law demonstrates the direct relationship between orbital speed, distance from the Sun, and the Sun's mass.
2.
Question 3
Explain how the accretion model accounts for the differences between the rocky planets and the gas giants in our Solar System. Your explanation must address the role of gravity, the composition of the interstellar cloud, and the formation of the accretion disc.
The accretion model explains the difference between rocky planets and gas giants by considering the temperature gradient within the original solar nebula and the subsequent accretion process. Gravity was the fundamental force driving the collapse of the nebula and the formation of the planets. The composition of the interstellar cloud was crucial; it contained varying amounts of elements depending on location.
In the inner Solar System, closer to the protosun, temperatures were high. Only materials with high melting points, such as metals and silicates, could condense into solid particles. These particles then accreted to form planetesimals, which eventually grew into the rocky planets. The lack of volatile substances meant that these planetesimals could not accumulate large amounts of gas.
In the outer Solar System, further from the protosun, temperatures were much lower. This allowed volatile substances like water, ammonia, and methane to freeze and condense. These icy particles, along with rocky material, could accrete to form larger planetesimals. The larger planetesimals had stronger gravitational pulls, enabling them to attract vast amounts of hydrogen and helium gas from the surrounding nebula. This led to the formation of the gas giants (Jupiter and Saturn) and ice giants (Uranus and Neptune), which are primarily composed of gas and ice. The accretion disc provided a continuous supply of material, allowing these planets to grow to their large sizes. The gravitational influence of the Sun and the planets themselves also played a role in shaping the final configuration of the Solar System.
3.
Data from a probe orbiting a newly discovered planet, Xylos, is presented below. The data includes the orbital distance from the planet's centre, the time taken for one orbit, the planet's mass, and the calculated surface temperature.
Orbital Distance (m) | Orbital Duration (s) | Planet Mass (kg) | Surface Temperature (K)
1.4 x 108 | 2.5 x 106 | 2.0 x 1027 | 500
2.8 x 108 | 5.0 x 106 | 2.0 x 1027 | 450
3.5 x 108 | 7.5 x 106 | 2.0 x 1027 | 400
Analyze the data and determine the relationship between the orbital distance and the surface temperature of Xylos. State your assumptions.
Answer: The data suggests an inverse relationship between orbital distance and surface temperature. As the orbital distance from the planet increases, the surface temperature decreases. This is because the gravitational pull is weaker at greater distances, resulting in less energy being absorbed from the planet.
Assumptions:
- The planet Xylos is roughly spherical.
- The planet's energy output is relatively constant.
- The planet's albedo (reflectivity) is constant.
- The probe is in a stable orbit and the orbital period is accurately measured.
Explanation: The temperature of a planet is influenced by the amount of energy it receives from its star. The amount of energy received depends on the distance from the star, which is related to the orbital distance. A smaller orbital distance means more energy received, leading to a higher surface temperature. The provided data, with increasing orbital distance and decreasing temperature, supports this relationship. The constant mass of the planet indicates that the energy output is not the primary factor influencing the temperature change in this scenario.