What type of wave has particles push together and pull apart?

when wave propagate through the medium the medium particles have two type of possible motions

1) Transverse Waves : here medium particles will move perpendicular to wave propagation and they pull and push perpendicular to the length

2) Longitudinal wave : here medium particles will move to and fro along the length of the medium and the medium particles will push and pull together along the length of the string.

So here in two types of wave motion it will depends on the medium type as well as it will depend on the source how is wave produced.

So the given type of wave in which particles push together and pull apart the wave must be longitudinal wave.

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.