Answer: Black hole.
Explanation:
As the massive star "compacts" under its own gravity, it triggers a massive supernova, after this point the remains of the star can become a neutron star, which is a very compact star made primarily, as the name says, of neutrons. The other possibility is a black hole, which is a finite region of space wherein it's interior there is a big concentration of mass, which creates a gravitational field strong enough that there is no particle that can escape it.
Answer:
The Moon revolves or moves around the Earth in a path called its orbit and rotates, or spins, in space.
Explanation: The Moon's movements cause the phases of the Moon and the Earth's ocean tides.
Answer:

Explanation:
When the rock is immersed in unknown liquid the forces that act on it are shown as under
1) Tension T by the string
2) Weight W of the rock
3) Force of buoyancy due to displaced liquid B
For equilibrium we have 
=
When the rock is suspended in air for equilibrium we have

When the rock is suspended in water for equilibrium we have
+
=
Using the given values of tension and solving α,β,γ simultaneously for
we get

Solving for density of liquid we get


Answer:
Emec = 94050 [J]
Explanation:
In order to solve this problem, we must understand that all thermal energy is converted into mechanical energy.
The thermal energy can be calculated by means of the following expression.

where:
Q = heat [J]
Cp = specific heat of water = 4186 [J/kg*°C]
m = mass = 300 [g] = 0.3 [kg]
T_final = 95 [°C]
T_initial = 20 [°C]
Now we can calculate the heat, replacing the given values:
![Q=0.3*4180*(95-20)\\Q= 94050[J]](https://tex.z-dn.net/?f=Q%3D0.3%2A4180%2A%2895-20%29%5C%5CQ%3D%2094050%5BJ%5D)
Since all this energy must come from the mechanical energy delivered by the exercise bike, and no energy is lost during the process, the mechanical energy must be equal to the thermal energy.
![Q=E_{mec}\\E_{mec}=94050[J]](https://tex.z-dn.net/?f=Q%3DE_%7Bmec%7D%5C%5CE_%7Bmec%7D%3D94050%5BJ%5D)