The increasing temperature of the core of a collapsing cloud of gas is due to
A collisions between gas molecules.
B increased spin rate of the cloud.
C fragmentation of the core.
D radiation.
The correct answer and explanation is:
The correct answer is A: collisions between gas molecules.
As a cloud of gas collapses under its own gravity, the particles within the cloud are drawn closer together. As the gas molecules collide with each other more frequently and with higher velocity, they convert kinetic energy into heat. This process increases the temperature of the gas, causing the core of the collapsing cloud to heat up. These collisions happen because as the particles move faster in a denser environment, the frequency of their interactions also rises. The energy released from these collisions directly raises the temperature in the center of the cloud.
The increasing temperature in the core of a collapsing gas cloud is a fundamental part of the formation of stars. When the core temperature reaches a certain threshold (millions of degrees), nuclear fusion can begin, which marks the birth of a star. During the initial stages of collapse, the cloud does not have enough heat from radiation or fusion to prevent further collapse, and so the energy generated by molecular collisions becomes the dominant source of temperature increase.
While B (increased spin rate of the cloud) can affect the dynamics of the cloud’s collapse and might lead to the formation of a rotating disk, it is not the primary cause of the temperature increase in the core.
C (fragmentation of the core) refers to the cloud breaking into smaller pieces, which can happen during collapse, but it does not directly lead to the temperature increase—collisions between particles do.
D (radiation) does play a role in the cooling of a cloud, as energy radiates away, but it is the collisions between gas molecules that primarily contribute to the core’s temperature increase during the collapse.
Thus, the temperature rise is a direct result of the kinetic energy from molecular collisions within the gas cloud.