How high will a 1.30-kg rock go from the point of release if thrown straight up by someone who does 80.0 j of work on it? neglect air resistance.

Explanation:

The work done on the stone is kinetic energy.

Kinetic energy = 80 J

We have

        Kinetic energy = 0.5 x Mass x Velocity²

        Mass = 1.30 kg

       80 = 0.5 x 1.30 x Velocity²

       Velocity = 11.09 m/s

We have equation of motion v² = u² + 2as

Initial velocity, u = 11.09 m/s  

Acceleration, a = -9.81 m/s²  

Final velocity, v = 0 m/s  

Substituting  

v² = u² + 2as

0² = 11.09² + 2 x -9.81 x s

s = 6.27 m  

Height it will go is 6.27 m

powerful computers now, not then

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.