Let
M = the mass of the planet
n = the mass of the satellite.
r = the radius of the planet
When the satellite is at a distance r from the surface of the planet, the distance between the centers of the two masses is 2r.
The gravitational force between them is

where
G = the gravitational constant.
When the satellite is on the surface of the planet, the distance between the two masses is r.
The gravitational force between them is

Answer:
Missing part in the text of the problem:
"<span>Water is exposed to infrared radiation of wavelength 3.0×10^−6 m"</span>
First we can calculate the amount of energy needed to raise the temperature of the water, which is given by

where
m=1.8 g is the mass of the water

is the specific heat capacity of the water

is the increase in temperature.
Substituting the data, we find

We know that each photon carries an energy of

where h is the Planck constant and f the frequency of the photon. Using the wavelength, we can find the photon frequency:

So, the energy of a single photon of this frequency is

and the number of photons needed is the total energy needed divided by the energy of a single photon:
Answer:
After a nucleus with 85 protons undergoes alpha decay, it has 83 protons.
Explanation:
In an alpha particle there are two protons
In the given substance's nucleus, there are total of 85 protons
After the decay, the proton number reduce
The current proton number after decay is
85 -2 = 83
After a nucleus with 85 protons undergoes alpha decay, it has 83 protons.
By Newton's Law of Universal Gravitation.
F = GMm/r²
Where F is Force of Gravitation, M = Mass of first object, m = mass of second object, r = distance of separation
From the formula, you can see that if the masses, M and m, increased, the value of F would definitely increase as well.
And if r increased the value of F would be reduced because you would be dividing by a bigger number, but when the value of r is decreased the value of F would be increased, because you would then be dividing by something smaller. Note the r is at the denominator of the formula.
So F would increase if there was increase in Masses and decrease in distance.
So the answer is C. a and b.