Answer:
r = 16 Km
Explanation:
given
m_n= 1.67 x 10^-27 Kg
M_star = 3.88 x 10^30 Kg
A= M_star/m_n
A= 3.88*10^30/1.67 x 10^-27
A=2.28 *10^57 neutrons A = The number of neutrons
we use the number of neutrons as a mass number because the star has only neutrons. = 1.2 x 10-15 m
r = r_o*A^1/3
r = 1.2*10^-15*2.28 *10^57^1/3
r = 16 Km
The freezing point of the water is 0 C , and it equals to 273 K
Then, To convert from Kelvins degrees to Celsius degrees we use the relation

Also,

A) d. 10T
When a charged particle moves at right angle to a uniform magnetic field, it experiences a force whose magnitude os given by

where q is the charge of the particle, v is the velocity, B is the strength of the magnetic field.
This force acts as a centripetal force, keeping the particle in a circular motion - so we can write

which can be rewritten as

The velocity can be rewritten as the ratio between the lenght of the circumference and the period of revolution (T):

So, we get:

We see that this the period of revolution is directly proportional to the mass of the particle: therefore, if the second particle is 10 times as massive, then its period will be 10 times longer.
B) 
The frequency of revolution of a particle in uniform circular motion is

where
f is the frequency
T is the period
We see that the frequency is inversely proportional to the period. Therefore, if the period of the more massive particle is 10 times that of the smaller particle:
T' = 10 T
Then its frequency of revolution will be:

Answer:
The time taken will be 0.553 seconds.
Explanation:
We should start off by finding the force exerted by the rope on the 3kg weight in this case.
Weight of 5kg mass = 5 * 9.81 = 49.05 N
Weight of 3kg mass = 3 * 9.81 = 29.43 N
The force acting upward on the 3kg mass will equal the weight of the 5kg mass. Thus the resultant force acting on the 3kg mass is:
Total force = 49.05 - 29.43 = 19.62 N (upwards)
We can now find the acceleration:
F = m * a
19.62 = 3 * a
a = 6.54 m/s^2
We now use the following equation of motion to get the time taken to travel 1 meter:


t = 0.553 seconds