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CLASS 11 PHYSICS CHAPTER 5 – WORK, ENERGY AND POWER

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  NCERT CLASS 11 PHYSICS CHAPTER 5 – WORK, ENERGY AND POWER IN-TEXT QUESTIONS AND ANSWERS 1. What is work in physics? Work is said to be done when a force acting on a body produces displacement in it. For a constant force: W = F s cos θ Where: W = work done F = applied force s = displacement θ = angle between force and displacement The SI unit of work is joule (J). 2. When is work done by a force positive? Work is positive when the force has a component in the direction of displacement. For example, when a person lifts a bag vertically upwards, the applied force and displacement are in the same direction. W = Fs cos 0° W = Fs 3. When is work done by a force negative? Work is negative when the force acts opposite to the direction of displacement. For example, friction does negative work on a moving body because friction acts opposite to its motion. W = Fs cos 180° W = −Fs 4. When is work done by a force zero? Work done is zero in the following situations: When there is no displaceme...
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CLASS 11 PHYSICS CHAPTER 6 – SYSTEM OF PARTICLES AND ROTATIONAL MOTION

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  NCERT CLASS 11 PHYSICS CHAPTER 6 – SYSTEM OF PARTICLES AND ROTATIONAL MOTION IN-TEXT QUESTIONS AND ANSWERS 1. What is a system of particles? A system of particles is a collection of two or more particles considered together for studying their motion and physical properties. Examples include: A group of atoms forming a molecule. A group of objects connected together. A rotating rigid body. 2. What is a rigid body? A rigid body is an ideal body in which the distance between any two particles remains constant, even when external forces act on it. In other words, a rigid body does not change its shape or size during motion. 3. What is the centre of mass? The centre of mass is the point at which the entire mass of a system can be considered to be concentrated for describing its translational motion. For a system of particles: R = (m₁r₁ + m₂r₂ + ... + mₙrₙ)/(m₁ + m₂ + ... + mₙ) 4. Where is the centre of mass of a uniform circular ring? The centre of mass of a uniform circular ring lies...
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