A. 
The orbital speed of the clumps of matter around the black hole is equal to the ratio between the circumference of the orbit and the period of revolution:
where we have:
is the orbital speed
r is the orbital radius
is the orbital period
Solving for r, we find the distance of the clumps of matter from the centre of the black hole:
B. 
The gravitational force between the black hole and the clumps of matter provides the centripetal force that keeps the matter in circular motion:
where
m is the mass of the clumps of matter
G is the gravitational constant
M is the mass of the black hole
Solving the formula for M, we find the mass of the black hole:
and considering the value of the solar mass
the mass of the black hole as a multiple of our sun's mass is
C. 
The radius of the event horizon is equal to the Schwarzschild radius of the black hole, which is given by
where M is the mass of the black hole and c is the speed of light.
Substituting numbers into the formula, we find
Answer:
A. 51.42 m.
B. 17.14 s.
Explanation:
Using equations of motion:
vf^2 = vi^2 + 2 * aS
Where,
vf = final velocity
a = acceleration
S = distance to which swan traveled
vi = 0 m/s
6.00^2 = 2 * 0.350S
S = 36/0.7
= 51.42 m.
B.
vf = vi + at
6 = 0 + 0.35t
t = 6/0.35
= 17.14 s.
The best answer is
C) reflecting telescope, because it can be made large enough to gather more radiations (or light) from distant objects.
Reflecting telescopes, unlike refracting telescopes, can be made larger and larger to collect more light, with more precision, from larger distances. Refracting telescopes generally are not used for any demanding purposes, such viewing objects in space by professional astronomers.
D.Atoms can be divided into smaller parts.
Dalton's atomic theory was the first complete attempt to describe allmatter in terms of atoms and their properties. Dalton based his theory on the law of conservation of mass and the law of constant composition. The first part of his theory states that allmatter is made of atoms, which are indivisible.
