A car moving with an initial velocity of 10 m/s slows down at a constant deceleration and stops after traveling 400 m. What is the time (in seconds) taken by the car to come to a stop?

A. 80 sec B. 60 sec


C. 25 sec D. 40 sec

Let's put kinematics to play, shall we?
Consider this equation:
v2u2=2
asv2−u2=2as ------- (1)
Here 'v' is the final velocity of the body in question
'u' is the initial velocity
'a' is the acceleration experienced, and
's' is the distance traveled.
Taking only S.I. units, for the case mentioned in the question, it can be calculated that a = -1/8 m/s/s (v = 0, u = 10, s = 400). The negative sign indicates that the body (the car) is decelerating.
Applying this result to another equation,
vu=a
tv−u=at -------- (2)
You can calculate the time taken (t) as t = -10/(-1/8).
Which is:
t = 80 seconds.

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