Abox of mass 1.0 kg compresses a spring of constant k = 1000 n/m. the spring and box are placed on a smooth horizontal surface and the spring is compressed by 15 cm. the box is released and spring relaxes causing the box to move away. the box encounters a rough patch of coefficient of friction μk=0.4 extending 2 meters. how fast is the box moving after it clears that patch?
a. 6.2 m/s
b. 4.7 m/s
c. 2.6 m/s
d. 7.4 m/s

option B

Explanation:

given,

mass of the box = 1 Kg

spring constant = k = 1000 N/m

spring is compressed upto = 15 cm = 0.15 m

coefficient of friction = μk =0.4

using conservation of energy

          v = 4.74 m/s

so, the velocity of the box = v = 4.74 m/s

hence, the correct answer is option B

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.

no sign of dia of fuel cell