In a shopping mall, two elevators pass each other moving in opposite directions. each elevator is moving at the same speed. the relative velocity of one elevator to another is 10 m/s. what is the velocity of each elevator to a person standing on the ground?

5 m/s upward and 5 m/s downward

Explanation:

Let's call v the speed of each elevator. So one elevator is moving with velocity +v relative to the ground (the positive sign indicates the upward direction) and the other one with velocity -v relative to the ground (downward direction).

The relative velocity of one elevator to another is 10 m/s, so we can write:

which means

So the speed of each elevator relative to the ground is 5 m/s, with one moving upward and the other one moving downward.

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.