A2000kg car experiences a braking force of 1n and skids to a stop in 6 seconds. the speed of the car just before the brakes were applied was
a) 45 m/s
b) 15 m/s
c) 1.2 m/s
d) 30 m/s
e) none of these
so far i got a= 5m/s^2 and u= 30m/s but i think the answer is 45 m/s but i do not know where to go from there.

D. 30m/s

Explanation:

According to the equation of motion

v=u +at

v = Final velocity

u = initial velocity

a = acceleration

t = time taken

Since we don't know the acceleration of the body, we will find its acceleration using newtons first law of motion F = ma

10000 =2000a

a = 5m/s²

initial velocity = 0m/s since the body starts from rest

v is what we are looking for

t = 6seconds

Substituting this datas in the formula

v = 0+ 5(6)

v = 30m/s (D)

the answer is b

explanation:

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.