Question

Name the type of motion in which a girl is skipping a rope at a particular spot
a) Rotatory motion
b) Periodic motion
c) Simple Harmonic motion
d) None

Answer 1

Since the girl is skipping a rope at a particular spot, we can say that the original position is repeated in some interval of time. So, consider the definitions of the given options and compare them with the situation.

Complete step by step answer:
a) Rotatory motion: Also known as rotational or circular motion, occurs only when an object rotates or spins about an axis.
Since the girl is not rotating about an axis, this option is wrong.

b) Periodic motion: It is the motion repeated in equal intervals of time. In this motion, the displacement of the object may or may not be in the direction of the restoring force.
Since the girl is having a jumping motion in equal intervals of time, the displacement may vary in each interval, depending on the energy of the girl. So, this motion is periodic motion. Hence, option (b) is the correct choice.

c) Simple Harmonic Motion: It is a special type of periodic motion where the restoring force on the moving object is directly proportional to the object's displacement magnitude and acts towards the object's equilibrium position.
Since the girl's displacement is not always acting in the opposite direction of the restoring force, the motion cannot me Simple Harmonic. So, option (c) is also wrong.

So, the correct answer is “Option B”.

Note:
Simple harmonic motion is similar to periodic motion, but the only difference is in the simple harmonic motion, the displacement of the object is always in the opposite direction of the restoring force. Therefore, all simple harmonic motions are periodic motion, but all periodic motions are not simple harmonic motion.