A body is said to be in motion if it changes its position with respect to time. The motion of the body depends on the external forces and surroundings. There are three types of motion seen in nature – rotatory motion, vibratory motion, and translatory motion.
A body is said to be at rest if it does not change its position with respect to time and surroundings. Every piece of matter, from the atoms to the entire earth, are in a continuous state of motion. Motion is clearly defined terms like Distance, Displacement, Time and Speed.
If the motion is repeated in regular interval of time, then it is referred to as periodic motion. The simple harmonic motion is a special kind of periodic motion.
Periodic motion Examples: oscillation of pendulum and motion of a swing.
As per the wave displayed above the motion is said to be periodic if the amplitude of the wave remains the same in all intervals of time.
Frequency is found by
Examples of Periodic Motion
Some of the best examples that display periodic motion are:
- Revolution of “earth” around the “sun” with a period of 1 year
- Rotation of earth about its axis with a time period of 24 hours (a day)
- Movement of the hour hand and minute hand in the clock.
- The rotation of “moon” around the “earth” with a time period 27.3 days
- The ticking of the clock
- Vibrating tuning fork
- The Bob of the pendulum
- The changing phase of the moon at a time period.
- A rocking chair
Centripetal and Centrifugal Force
Force is felt on the rotating objects or on the objects rotating in a circular path. Centripetal and centrifugal force are the types of force seen in a circular path. Centripetal force is a type of force that lets the object follow the circular path or is attracted towards the centre of the fixed point. The centripetal force was described by Christiaan Huygens in 1659, and Isaac Newton later defined centripetal force 25 years later in 1684.
The direction of movement in the centripetal force will always be inwards.
The above picture shows the direction of centripetal force and velocity
Centrifugal force is an inertia force where the object moving in a circular path experiences an outward force. It is dependent on the mass of the object and the distance of the object from the centre of the circle.
The direction of the object away from the circular path is showed in the figure above.
Centripetal and centrifugal force can be found through the formula
Fc = Centrifugal force
m = mass
v = speed
r = radius
Centripetal force examples are given below.
- Turning a car
- Spinning a ball on a string:
- Planets moving around the Sun along the orbit
Centrifugal Force Examples are given below.
- A bike making a turn.
- Vehicle driving around a curve
- The weight of an object at the poles and on the equator
For more information on various types of motion along with examples, refer BYJU’S