Question

Paheli moves on a straight road from point A to point C. She takes 20 minutes to cover a certain distance AB and 30 minutes to cover the rest distance BC. She then turns back and takes 30 minutes to cover the distance CB and 20 minutes to cover the rest of the distance to her starting point. She makes 5 rounds on the road the same way. Paheli concludes that her motion is

• A. only rectilinear motion
• B. only periodic motion
• C. rectilinear and periodic both
• D. neither rectilinear nor periodic

Answer 1

The correct option is C

rectilinear and periodic both

The explanation of the correct option

In the case of option C

1. The time taken by Paheli to travel the same distance is constant from A to B and B to C.
2. She returns to the same points B and A after a fixed interval of time. So, her motion is periodic since a periodic motion repeats after a fixed interval of time.
3. Paheli is travelling in a straight line along with ABC. So, her motion is rectilinear too since a body in rectilinear motion travels along a straight path.

The explanation of the incorrect option

In the case of option A

Paheli's motion is rectilinear. But it's not only a periodic motion. Her motion is periodic too.

In the case of option B

Paheli's motion is periodic. But it's not only a periodic motion. Her motion is rectilinear too.

In the case of option D

Paheli's motion is neither periodic nor rectilinear is not a true statement. As we have discussed above, her motion is periodic as well as rectilinear too.

Hence, option C is the correct answer.