The gravitational force of a star on an orbiting planet 1 is f1. planet 2, which is twice as massive as planet 1 and orbits at three times larger distance from the star, experiences gravitational force f2.
what is the ratio f2f1? you can ignore the gravitational force between the two planets.

ratio = 1 : 4.5

Explanation:

If m₁ is the mass of the star and m₂ the mass of the planet, the force of gravity F₁ for planet 1 is given by:

The force F₂:

The ratio:

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.

a.   mass number from atomic number