When a lift is accelerating downward that a=g then the net force acting on the object is: (a)F=0N (b)F=mg (c)F=w-mg (d) F=w_ma

the answers the correct one is A

 F = 0

Explanation:

To find the net force we must apply Newton's second law

           F -W = ma

where the upward direction is positive, they indicate that the acceleration is equal to = - g

           F = W - m g

the weight of a body of W = mg

   we substitute

           F = mg - mg

           F = 0

The check the answers the correct one is A

i don't know that i agree with that but what's the question ?

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.