A 58.0 g incoming tennis ball has a speed of 30 m/s when it is hit by a racket in the opposite direction and leaves the racket at 40 m/s. What
is the average force exerted by the racket on the ball if contact lasted
for 5.2 ms?

The racket applies an average acceleration of

(Note that I'm taking the initial direction of the ball's motion to be negative.)

Then the average force exerted on the ball is

a and b sometimes have a positive value

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.