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Class 9 Physics Chapter 2: Force and Laws of Motion - Formulas

🔹 Class 9 Science – Force and Laws of Motion (Chapter 9) 📘 Key Formulas Force (F) = Mass (m) × Acceleration (a) → F = m × a Momentum (p) = Mass (m) × Velocity (v) → p = m × v Newton’s Second Law (from momentum): → F = (mv - mu) / t Impulse = Force × Time → Impulse = F × t = Change in momentum Law of Conservation of Momentum: In a closed system (no external force), the total momentum before and after interaction remains constant. → m 1 u 1 + m₂u₂ = m 1 v 1 + m₂v₂ Where: m 1 , m₂ = masses of two bodies u 1 , u₂ = initial velocities v 1 , v₂ = final velocities Recoil Velocity (v r ): When a gun fires a bullet, the gun moves backward with recoil velocity due to conservation of momentum. → v r = -(m × v) / M Where: m = mass of bullet v = velocity of bullet M = mass of gun v r = recoil velocity of gun 🔁 Negative sign indicates direction opposite to bullet. Derivation of Recoil Velocity: According to t...

Class 9 Physics Chapter 1 Motion – All Formulas with Meanings and Units (CBSE Notes)

🚀 Class 9 Physics – Chapter 1: Motion – Important Formulas This chapter is based on basic concepts of motion in physics. Here are all the formulas you need to learn, along with their meaning and SI units. 📌 1. Speed Speed = Distance / Time Symbolically: v = d / t Speed (v) → m/s (meters per second) Distance (d) → meters (m) Time (t) → seconds (s) 📌 2. Velocity Velocity = Displacement / Time Symbolically: v = s / t Velocity (v) → m/s Displacement (s) → meters 📌 3. Average Speed Average Velocity = Total Displacement /Total Time Two important cases for calcualting average speed : If Total journey is divided into two equal parts with different speeds (v 1 and v 2 ) and distance are equal : Average Velocity = 2v 1 v 2 / v 1 +v 2 If Total journey is divided into two equal time intervals with different speeds (v 1 and v 2 ): V avg = (u + v ) / 2 Average Velocity (v) → m/s (meters per second) Distan...

Class 9 Physics Chapter 1: Motion – Questions and Answers (Theoretical)

🚀 Class 9 Physics Chapter 1: Motion – Questions and Answers (Theory Only) These questions are based on CBSE NCERT Class 9 Physics Chapter "Motion". These are fully theory-based and are designed for concept-building and exam preparation. No numerical problems included. 📘 1. Describing Motion What do you mean by the term "motion"? → Motion is the change in position of an object with respect to time and a reference point. Can an object be in motion for one observer and at rest for another? Explain. → Yes. Motion is relative. A person sitting in a train is at rest w.r.t the train but in motion w.r.t the ground. How can we say that motion is a continuous process? → Because even when an object appears to be at rest, its molecules are still in motion. Is motion always visible? → No. Motions like sound waves or atoms moving are invisible but real. Why is reference point important to describe motion? → Because motion is always measured relative to some fi...

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