Question

Which of the following is an example of oscillatory motion?
A) The heartbeat of a person
B) The motion of the earth around the sun
C) The motion of Halley’s comet around the sun
D) Oscillation of a simple pendulum

Answer 1

Hint: Oscillatory can be described as an object’s motion, where the object repeats its trajectory of motion continuously. In this motion, the associated object continuously tends to move to and fro along the same path. Theoretically, the object will tend to continue its motion forever, but in our world, friction eventually settles down the object to its equilibrium.

Complete solution:
The oscillatory motion has some unique qualities such as time-period, the total time taken by the object associated with the motion to come to the same position in its trajectory. The time-period of every oscillatory motion is unique because it helps find out the other quantities related to the motion. The other useful quantity is the motion’s frequency, usually expressed as the reciprocal of the time-period of the motion.
The heartbeat of a person is continuous, but it is not a motion at all. Furthermore, the heartbeat per minute can differ from person to person.
The motion of the earth and Halley’s comet around the sun indeed have an exact time-period, but these are rotatory motion and not oscillatory motion.
The oscillation of a simple pendulum is an oscillatory motion because it always has an exact value of time-period that depends on the length of the string of the pendulum. A simple pendulum moves to and fro along the same path for quite some time until the friction compels the object to settle down to its equilibrium position.

Note: The time-period of simple pendulum motion also depends on the gravitational acceleration of the earth’s position. Hence, we can use a simple pendulum with a known length of the string to determine the gravitational acceleration of a position on the earth.