Aparachutist bails out and freely falls 50 m. then the parachute opens, and thereafter she deceler- ates at 2.0 m/s2. she reaches the ground with a speed of 3.0 m/s. (a) how long is the parachutist in the air? (b) at what height does the fall begin?

a)The parachutist in the air for 12.63 seconds.

b)The parachutist falls from a height of 293 meter.

Explanation:

Vertical motion of  parachutist:

 Initial speed, u = 0m/s

 Acceleration, a = 9.81 m/s²

 Displacement, s = 50 m

 We have equation of motion, v² = u² + 2as

 Substituting

   v² = 0² + 2 x 9.81 x 50

    v = 31.32 m/s

 Time taken for this

          31.32 = 0 + 9.81 x t

            t = 3.19 s

 After 50m we have

 Initial speed, u = 31.32m/s

 Acceleration, a = -2 m/s²

 Final speed , v = 3 m/s

 We have equation of motion, v² = u² + 2as

 Substituting

   3² = 31.32² - 2 x 2 x s

    s = 243 m

 Time taken for this

          3 = 31.32 - 2 x t

            t = 9.44 s

a) Total time = 3.19 +  9.44 = 12.63 s

    The parachutist in the air for 12.63 seconds.

b) Total height = 50 + 243 = 293 m

    The parachutist falls from a height of 293 meter.

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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.