subject: Forced Oscillations And Resonance [print this page] The to and fro motion of a body about a mean position is called oscillation. When a body execute oscillations under the action of external periodic force, Those oscillations are called forced oscillations.
When one of the two bodies of same natural frequency is set into vibration, the other body also vibrates with larger amplitude under the influence of the first one. This phenomenon is called Resonance.
Take two hollow boxed A and B, open it one side. Place two boxes with their opened sides facing each other with some distance apart. Mount two tuning forks of same natural frequencies one each on the two boxes. Vibrate the tuning fork on the box A, the tuning fork on box B also begins to vibrate due to resonance. When A is vibrated, the air inside the box A vibrates and these vibrations are transferred into the box B and in turn vibrated the tuning fork on B.
Activity on Forced Oscillations and Resonance
Vibrate a tuning fork and place it on a table or bench, Then we can hear a loud sound which is because the table top is forced to vibrate under the influence of the vibrating tuning fork.
Suspend 4 pendulums A, B, C, D in which A and C are of same lengths, B and D are of different lengths. When Pendulum A is oscillated, the other three pendulum's also start oscillating. A and C are in Resonance with each other and the oscillations of B and D are called forced oscillations.
Examples : When solders are crossing a suspension bridge, they are asked to break their steps. This is because , when the frequency of the marching coincides with the natural frequency of the bridge, the bridge vibrates with larger amplitude and collapses due to resonance.
A radio is tuned to obtain a clear sound, such that the frequency of the radio have to coincide with the frequency of the incoming electro-magnetic waves.
Examples and Applications on Forced Oscillations and Resonance
When solders are crossing a suspension bridge, they are asked to break their steps. This is because , when the frequency of the marching coincides with the natural frequency of the bridge, the bridge vibrates with larger amplitude and collapses due to resonance.
A radio is tuned to obtain a clear sound, such that the frequency of the radio have to coincide with the frequency of the incoming electro-magnetic waves.
We can find the velocity of sound using resonance phenomenon with resonating air-column experiment.
