1st Year Physics Chapter 7 Notes

• Important 1st year physics chapter 7 short questions from Punjab Textbook.
• Oscillations: Many a times, we come across a type of motion in which a body moves to and fro about a mean position. It is called oscillatory or vibratory motion. The oscillatory motion is called periodic when it repeats itself after equal intervals of time. Some typical vibrating bodies are shown in Fig. 7.1. It is our common observation that a) a mass, suspended from a spring, when pulled down and then released, starts oscillating (Fig. 7.1 a), b) the bob of a simple pendulum when displaced from its rest position and released, vibrates (Fig. 7.1 b).  c) a steel ruler clamped at one end to a bench oscillates when the free end is displaced sideways (Fig. 7.1 c). d) a steel ball rolling in a curved dish, oscillates about its rest position (Fig. 7.1 d).
• Thus to get oscillations, a body is pulled away from its rest or equilibrium position and then released. The body oscillates due to a restoring force. Under the action of this restoring force, the body accelerates and it overshoots the rest position due to inertia. The restoring force then pulls it back. The restoring force is always directed towards the rest position and so the acceleration is also directed towards the rest or mean position.
• It is observed that the vibrating bodies produce waves. For example, a violin string produces sound waves in air. There are many phenomena in nature whose explanation requires the understanding of the concepts of vibrations and waves. Although many large structures, such as skyscrapers and bridges, appear to be rigid, they actually vibrate. The architects and the engineers who design and build them, take this fact into account.
• Instantaneous displacement and amplitude of vibration
• Vibration
• Time period and frequency
• Important 1st year physics chapter 7 important long questions from Punjab Textbook.
• Simple harmonic motion: Let us consider a mass m attached to one end of an elastic spring which can move freely on a frictionless horizontal surface as shown in Fig. 7.2 (a). When the mass is displaced towards right through a distance x (Fig. 7.2 b), the force Fat that instant is given by Hooke's law F = lox where k is a constant known as spring constant. Due to elasticity, spring opposes the applied force which produces the displacement. This opposing force is called restoring force F. which is equal and opposite to the applied force within elastic limit of the spring. Hence       F - kx
• The negative sign indicates that F, is directed opposite to x. Le., towards the equilibrium position. Thus we see that in a system obeying Hooke's law, the restoring force F. is directly proportional to the displacement x of the system from its equilibrium position and is always directed towards it. When the mass is released, it begins to oscillate about the equilibrium position (Fig. 7.2 c).
• Angular frequency
• SMH and uniform circular motion
• Displacement
• Important 1st year physics chapter 7 solved exercise from Punjab Textbook.
• Instantaneous velocity
• Acceleration in time of ω
• Phase
• A horizontal mass-spring system
• Spring pendulum
• Important 1st year physics chapter 7 numericals from Punjab Textbook.
• Energy conservation in SMS
• Free and forced oscillation
• Resonance
• Damped oscillation
• Sharpness of resonance
• Important 1st year physics chapter 7 conceptual questions from Punjab Textbook.