Question

A train is moving with a constant speed of 5 m/s and there are two persons A and B standing at aseparation of 10 m inside the train. Another person C is standing on the ground. A moves towards
B and back to its position in 10 seconds with constant speed. Then,
(A) displacement by A, in frame of reference of C is 50 m.
(B) distance covered by A, in frame of reference of C is 50 m.
(C) displacement by A, in frame of reference of train is 25 m.
(D) distance covered by A, in frame of reference of C is 25 m.

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Answer 1

The distance covered by A with reference to C is 50m. And option 'B'is correct.

Given:-

Speed of the train = 5m/s

Distance between two persons in train = 10m

To Find:-

The distance or displacement covered by A with reference to C.

Solution:-

We can easily calculate the value of distance or displacement covered by A with reference to C by using these simple steps.

As

Speed of the train (vt) = 5m/s

Distance between two persons in train (d) = 10m

Speed of train with to A (va) = 2m/s

So, total speed of train in first five seconds,

v = vt + va

v = 5 + 2

v = 7m/s

And total speed of train in last five seconds,

v = vt - va

v = 5 - 2

v = 3m/s

Now, According to the formula,

$speed \: = \frac{distance}{time}$

so,

$distance \: = speed \times time$

for first five seconds,

$d1 = 7 \times 5$

$d1 = 35m$

for last five seconds,

$d2 = 3 \times 5$

$d2 = 15m$

Total distance covered = d

$d = d1 + d2$

$d = 35 + 15$

$d = 50m$

Hence, The distance covered by A with reference to C is 50m. And option 'B'is correct.

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