Answer:
Stellar black holes form when the center of a very massive star collapses in upon itself.
Answer:
Light of a shorter wavelength should be used.
Explanation:
This is studied in the phenomenon called photoelectric effect, in which light is able to release electrons from a metal, said electrons are called photoelectrons .
The experiments that have been carried out show that <u>increasing or decreasing the intensity of the light will not cause the photoelectrons to be emitted</u>, what will cause the photoelectrons to be emitted is to increase the frequency of the incident light.
And a higher frequency corresponds to a shorter wavelength according to the equation:

(where
is frequency,
the speed of light, and
the wavelength)
So the answer is that the wavelength of the light must be shortened to cause the emission of electrones.
Answer:
25m/s
Explanation:
here we use 1st equation of motion
then we find this ans
The speed downwards is 7 + (3*9.8)
7+ 29.4 = 36.4 m/s