Verified Answer :

AL2006

The way I look at these things is like this:

-- The runner covered 12 meters in 4 seconds.
Average speed = 3 meters per second.

-- Speed at the beginning = zero.
In order to make the average 3, Speed at the end = 6 meters per second.

-- Speed increased from zero to 6 meters per second in 4 seconds.
It must have increased 1.5 meters per second each second.

That's choice-#2.

sairah

Here we have - 
Acceleration (a) = ?
Initial velocity (u) = 0 m/s (runner starts from rest)
Distance (s) = 12 m
Time (t) = 4 seconds

So, using the second equation of motion, we have-

\(s = ut + \frac{1}{2}at^{2}\)

\(12 = 0*4 + \frac{1}{2}*a*4 ^{2}\)

\(12 = 0+8a\)

\(\frac{12}{8} = a\)

\(1.5m/ s^{2}\)

So, option (2) is correct.

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