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)

f=ma newton

f=100x2.5=250n