The study of harmonic motion is important in determining the scientific effect of some natural phenomena. In most cases, particles possess both internal and external characteristics that demonstrate their behavior and the reason they adapt to some unique characters. These behavioral characteristics are normally associated with some forces that tend to align them towards a given central position. For instance, simple harmonic force, which forms many world known devices, has had impact on the formation and the activity of these devises. This paper deals with the simple harmonic motion and gives two real world devices that utilize the concept of SHM by describing the nature of the harmonic motion in these devices. It also discusses the application of the motion in the planetary orbit model in highlighting the source of centripetal force.

According to Jha (2006), simple harmonic motion (SHM) is normally the form of periodic motion of a given mass of a particle on a string that is subjected to linear elastic force. He points out that this restoring force normally acts according to Hooke’s law. He further states that any given mass that undergoes simple harmonic motion must experience an acting force on it which is proportional to its acceleration. This is in relation to Hooke’s law which determines that the restoring force that displaces a given mass in an oscillatory motion from its equilibrium position must be proportional to the displacement unless the elastic limit is not exceeded.

Jha (2006) points out that in the simple harmonic motion, it is assumed that the pendulum string in the SHM model is normally massless. This stipulates that the oscillation, which comes as a result, is primarily caused by the force that only acts on the mass of the object attached to the string or spring. Moreover, the SHM model system is assumed to be frictionless and, hence, presents only the restoring force acting on the object as the main cause of the harmonic motion.

The model of simple harmonic motion has normally been applied, for instance, in the oscillation of a buoy due to the effect of wave motion; thus, the nature of the wave motion can be understood. Other devices that also apply simple harmonic motion are the pendulum clocks and torque variation control devices in vehicles. These devices move in an oscillatory motion at a small angle due to the point mass that dictates the displacement of the device under gravitational force. Therefore, gravitational force is the restoring force that tends to be aligned with the both devices in order to counter the acceleration force caused by mechanical or chemical energy. This enables the devices to accelerate in speed that is proportional to the force applied to a given distance (Ostdiek & Bord, 2009).

Centripetal Force

On the other hand, a planetary orbit, such as of the Sun or of the Earth, tends to emulate the principle of simple harmonic motion, especially through the effect of centripetal force. As pointed out by Coffey (2010), the gravitational force acting between the Sun and the Earth is the main source of centripetal force that keeps our planet on its orbit. He notes that the centripetal force is the constant force acting on the Earth by displacing it towards the center of a circular path, thereby creating circular motion.

According to DeBoer and Smith (2009), the shape of the Earth’s orbit is normally oval. They note that this eclipsed shape of the Earth’s orbit is a result of varying daily distance between our planet and the Sun.  They further point out that the angle of inclination of the Earth’s axis at the orbital plane from the Sun is another factor that has contributed to the oval shape of its orbit. This shows that there is no uniformity of the centripetal force’s impact that pushes the Earth to the centre of the circular path.

As DeBoer and Smith (2009) point out, the discovery by Johannes Kepler that the orbit of Mars is not a perfect circle led to the formulation of the planetary motion law. They note that both the first and second Kepler’s laws denoted the variation in the speed of Mars at the orbit which was adversely controlled by the force from the Sun. Therefore, it led to the innovation that there is a gravitational force that keeps the Earth moving in circular motion around the Sun. This is what in turn led to scientific revolution.


In conclusion, the write-up has pointed to the concept of simple harmonic motion as the main cause of inventing useful devices. It has also noted the need for the scientists to apply their scientific model in simplifying the real events that have resulted into the formation of the planetary Earth.

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