If this speed is based on what would be safe in wet weather, estimate the radius of curvature for a curve marked 45 km/hkm/h . the coefficient of static friction of rubber on wet concrete is î¼s=0.7î¼s=0.7, the coefficient of kinetic friction of rubber on wet concrete is î¼k=0.5î¼k=0.5

 r = 22.78 m

Explanation:

For this exercise let's use Newton's second law

Axis y

                 N- W = 0

                 N = W

X axis

                F = m a

Where the acceleration is centripetal

               a = v² / r

The force is the friction that the formula has

               fr = μ N

               fr = μ mg

Let's replace

            μ m g = m v² / r

           r = v² / μ g

Let's reduce the speed to the SI system

         v = 45 km / h (1000 m / 1 km) (1h / 3600 s) = 12.5 m / s

          r = 12.5 2 / (0.7 9.8)

          r = 22.78 m

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.