Question 1: Define a nebula and explain its role in the life cycle of stars.

Answer: A nebula is a large cloud of gas and dust in space that serves as the birthplace of stars, where gravity causes the material to clump together and form new stars.

Question 2: Describe the process by which a star becomes a black hole.

Answer: A massive star exhausts its fuel, collapses under gravity after a supernova explosion, and if its remaining core is sufficiently dense, it forms a black hole.

Question 1: What is nuclear fusion and why is it important in stars?

Answer: Nuclear fusion is the process where atomic nuclei combine to form a heavier nucleus, releasing energy; it is the source of a star's light and heat.

Question 2: Explain the significance of a supernova in the formation of black holes.

Answer: A supernova is a massive explosion marking the death of a star, which can leave behind a dense core that may become a black hole if sufficiently massive.

Question 1: A star has a mass of 10 times that of our Sun. If the Sun's mass is 1.989 x 10^30 kg, what is the mass of the star? (Use the formula: Mass of star = number of solar masses x mass of Sun).

Answer: 1.989 x 10^31 kg

Question 2: Calculate the approximate density (kg/m^3) of a black hole with a mass of 5 solar masses and a radius of 10 km. Use the volume formula for a sphere: V = (4/3)πr^3. (Note: Density = mass/volume).

Answer: Approximate density = 2.38 x 10^18 kg/m^3

Question 1: Design a simple theoretical experiment to demonstrate the effect of gravity on star formation in a laboratory setting. List the variables and safety precautions involved.

Answer: A hypothetical experiment could involve using a large transparent container filled with a mixture of small particles and a fluid to simulate gas clouds, and applying varying gravitational forces using weights or magnetic fields. Variables include particle density, gravitational force, and fluid viscosity. Safety precautions involve handling weighted objects carefully to avoid injury and ensuring the setup is stable.

Question 1: A star begins as a nebula, then progresses to a main sequence star, followed by a supernova, and finally becomes a black hole. If the initial nebula has a temperature of 10,000 K and the black hole's event horizon temperature is near absolute zero, explain the temperature changes during this process.

Answer: The temperature decreases significantly from the hot nebula to the cold black hole. Initially, gravity causes gas to heat up in the nebula, but as the star exhausts fuel and collapses, the outer layers cool, and the black hole's event horizon emits near-zero thermal radiation due to its extreme gravity and lack of thermal emission.

Question 1: Describe the main differences between a white dwarf, a neutron star, and a black hole in terms of their formation and physical properties. (6 marks)

Answer: White dwarfs are remnants of medium-sized stars that have shed their outer layers, characterized by high density but limited mass. Neutron stars form from supernova explosions of massive stars, are incredibly dense with a radius of about 10 km, and consist mostly of neutrons. Black holes result from the collapse of very massive stars after supernova, possessing an event horizon from which nothing can escape, and have a mass that can be several times that of the Sun.

Question 1: How does understanding black holes contribute to advancements in technology or industry?

Answer: Studying black holes improves our understanding of gravity and spacetime, which can lead to advancements in GPS technology, satellite communication, and the development of new materials resistant to extreme conditions.