A ball initially at rest is dropped from an unknown height. Right before the ball hits the ground, it reaches a velocity of 30 m/s. Assuming air resistance is negligible, calculate the initial height of the object. A.
15 m
B.
30 m
C.
45 m
D.
75 m

45m

Explanation

Using third equation of motion which's vf^2 - vi^2 = 2gh in case of vertical motion so ,

step 1 : (30)^2 - (0)^2 =  2(10) h

step 2 : 900 = (20)h

step 3 : 900/20 = h

the answer is kevlar

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.