What is "Energy" ? āĻļāĻ•ā§āϤāĻŋ ?


Energy (āĻļāĻ•ā§āϤāĻŋ) : Energy is the capacity to do work. āĻļāĻ•ā§āϤāĻŋ āĻšā§ˆāϛ⧇ āĻ•āĻžāĻŽ āϕ⧰āĻžā§° āĻ•ā§āώāĻŽāϤāĻžāĨ¤


Law of Conservation of Energy : āĻļāĻ•ā§āϤāĻŋ āϏāς⧰āĻ•ā§āώāĻŖā§° āύ⧀āϤāĻŋ


Energy cannot be created or destroyed, but it can change from one form to another. āĻļāĻ•ā§āϤāĻŋ āϏ⧃āĻˇā§āϟāĻŋ āĻŦāĻž āĻ§ā§āĻŦāĻ‚āϏ āϕ⧰āĻŋāĻŦ āĻ¨ā§‹ā§ąāĻžā§°āĻŋ, āĻ•āĻŋāĻ¨ā§āϤ⧁ āχ āĻāϟāĻž ā§°ā§‚āĻĒā§° āĻĒā§°āĻž āφāύ āĻāϟāĻž ā§°ā§‚āĻĒāϞ⧈ āĻĒā§°āĻŋāĻŦā§°ā§āϤāĻŋāϤ āĻš’āĻŦ āĻĒāĻžā§°ā§‡āĨ¤


Gravitational Potential Energy : āĻŽāĻšāĻžāĻ•āĻ°ā§āώ⧀āϝāĻŧ āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ : Gravitational potential energy is the energy possessed by an object due to its height above the ground. āĻŽāĻšāĻžāĻ•āĻ°ā§āώ⧀āϝāĻŧ āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āĻšā§ˆāϛ⧇ āϕ⧋āύ⧋ āĻŦāĻ¸ā§āϤ⧁⧰ āĻŽāĻžāϟāĻŋā§° āĻ“āĻĒā§°āϤ āĻĨāĻ•āĻž āωāĻšā§āϚāϤāĻžā§° āĻŦāĻžāĻŦ⧇ āϞāĻžāĻ­ āϕ⧰āĻž āĻļāĻ•ā§āϤāĻŋāĨ¤


Formula / āϏ⧂āĻ¤ā§ā§° : PE = mgh


Where / āϝ’āϤ : m = mass (āĻ­ā§°), g = acceleration due to gravity (āĻŽāĻšāĻžāĻ•āĻ°ā§āώ⧀āϝāĻŧ āĻ¤ā§āĻŦā§°āĻŖ),  h = height (āωāĻšā§āϚāϤāĻž)


Kinetic Energy : āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ


Kinetic energy is the energy possessed by an object due to its motion. āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āĻšā§ˆāϛ⧇ āϕ⧋āύ⧋ āĻŦāĻ¸ā§āϤ⧁⧰ āĻ—āϤāĻŋā§° āĻŦāĻžāĻŦ⧇ āϞāĻžāĻ­ āϕ⧰āĻž āĻļāĻ•ā§āϤāĻŋāĨ¤


Formula / āϏ⧂āĻ¤ā§ā§° : KE =1/2mv2


Where / āϝ’āϤ: = mass (āĻ­ā§°),  = speed or velocity (āĻŦ⧇āĻ—)


Relation Between Potential and Kinetic Energy (āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āφ⧰⧁ āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋā§° āϏāĻŽā§āĻĒā§°ā§āĻ•)


Gain in kinetic energy is equal to loss in potential energy. (āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋā§° āĻŦ⧃āĻĻā§āϧāĻŋ āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋā§° āĻšā§ā§°āĻžāϏ⧰ āϏāĻŽāĻžāύāĨ¤)


Work (āĻ•āĻžāĻŽ)


Work is done when a force moves an object through a distance in the direction of the force. āĻŦāϞ⧰ āĻĻāĻŋāĻļāϤ āϕ⧋āύ⧋ āĻŦāĻ¸ā§āϤ⧁ āύāĻŋāĻ°ā§āĻĻāĻŋāĻˇā§āϟ āĻĻā§‚ā§°āĻ¤ā§āĻŦ āϞ⧈ āĻ—āϤāĻŋ āϕ⧰āĻŋāϞ⧇ āĻ•āĻžāĻŽ āϏāĻŽā§āĻĒāĻ¨ā§āύ āĻšāϝāĻŧāĨ¤


Formula / āϏ⧂āĻ¤ā§ā§° : W = F × d


Where / āϝ’āϤ : = Work (āĻ•āĻžāĻŽ), = Force (āĻŦāϞ), = Distance moved (āĻĻā§‚ā§°āĻ¤ā§āĻŦ)


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Energy – 2 Marks Questions with Answers : āĻļāĻ•ā§āϤāĻŋ – ⧍ āύāĻŽā§āĻŦā§°ā§° āĻĒā§ā§°āĻļā§āύ⧋āĻ¤ā§āϤ⧰


1. State the law of conservation of energy. āĻļāĻ•ā§āϤāĻŋ āϏāς⧰āĻ•ā§āώāĻŖā§° āύ⧀āϤāĻŋ āωāĻ˛ā§āϞ⧇āĻ– āϕ⧰āĻžāĨ¤


Ans: Energy cannot be created or destroyed, but it can change from one form to another. āωāĻ¤ā§āϤ⧰: āĻļāĻ•ā§āϤāĻŋ āϏ⧃āĻˇā§āϟāĻŋ āĻŦāĻž āĻ§ā§āĻŦāĻ‚āϏ āϕ⧰āĻŋāĻŦ āĻ¨ā§‹ā§ąāĻžā§°āĻŋ, āĻ•āĻŋāĻ¨ā§āϤ⧁ āĻāϟāĻž ā§°ā§‚āĻĒā§° āĻĒā§°āĻž āφāύ āĻāϟāĻž ā§°ā§‚āĻĒāϞ⧈ āĻĒā§°āĻŋāĻŦā§°ā§āϤāĻŋāϤ āĻš’āĻŦ āĻĒāĻžā§°ā§‡āĨ¤


2. What is kinetic energy ? Write its formula. āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āĻ•āĻŋ ? āχāϝāĻŧāĻžā§° āϏ⧂āĻ¤ā§ā§° āϞāĻŋāĻ–āĻžāĨ¤


Ans: Kinetic energy is the energy possessed by a body due to its motion. (āϕ⧋āύ⧋ āĻŦāĻ¸ā§āϤ⧁⧰ āĻ—āϤāĻŋā§° āĻŦāĻžāĻŦ⧇ āϞāĻžāĻ­ āϕ⧰āĻž āĻļāĻ•ā§āϤāĻŋāĻ• āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āĻŦā§‹āϞāĻž āĻšāϝāĻŧāĨ¤)





 KE = 1/2mv2


3. What is gravitational potential energy ? āĻŽāĻšāĻžāĻ•āĻ°ā§āώ⧀āϝāĻŧ āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āĻ•āĻŋ ?


Ans: Gravitational potential energy is the energy possessed by a body due to its height above the ground. āωāĻ¤ā§āϤ⧰: āĻŽāĻžāϟāĻŋā§° āĻ“āĻĒā§°āϤ āĻĨāĻ•āĻž āωāĻšā§āϚāϤāĻžā§° āĻŦāĻžāĻŦ⧇ āϕ⧋āύ⧋ āĻŦāĻ¸ā§āϤ⧁āϤ āϏāĻžā§āϚāĻŋāϤ āĻļāĻ•ā§āϤāĻŋāĻ• āĻŽāĻšāĻžāĻ•āĻ°ā§āώ⧀āϝāĻŧ āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āĻŦā§‹āϞāĻž āĻšāϝāĻŧāĨ¤


4. Write the formula of work done. āĻ•āĻžāĻŽā§° āϏ⧂āĻ¤ā§ā§° āϞāĻŋāĻ–āĻžāĨ¤


Ans: W = F×d . Work done is equal to force multiplied by distance moved in the direction of force. āωāĻ¤ā§āϤ⧰: āĻŦāϞ āφ⧰⧁ āĻŦāϞ⧰ āĻĻāĻŋāĻļāϤ āĻ…āϤāĻŋāĻ•ā§ā§°āĻŽ āϕ⧰āĻž āĻĻā§‚ā§°āĻ¤ā§āĻŦā§° āϗ⧁āĻŖāĻĢāϞāĻ• āĻ•āĻžāĻŽ āĻŦā§‹āϞāĻž āĻšāϝāĻŧāĨ¤


5. What happens to potential energy when kinetic energy increases ? āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āĻŦ⧃āĻĻā§āϧāĻŋ āĻĒāĻžāϞ⧇ āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋā§° āĻ•āĻŋ āĻšāϝāĻŧ ?


Ans: When kinetic energy increases, potential energy decreases. āωāĻ¤ā§āϤ⧰: āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āĻŦ⧃āĻĻā§āϧāĻŋ āĻĒāĻžāϞ⧇ āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āĻšā§ā§°āĻžāϏ āĻĒāĻžāϝāĻŧāĨ¤


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Energy – 5 Marks Questions with Answers : āĻļāĻ•ā§āϤāĻŋ – ā§Ģ āύāĻŽā§āĻŦā§°ā§° āĻĒā§ā§°āĻļā§āύ⧋āĻ¤ā§āϤ⧰


1. Explain the law of conservation of energy with an example. āωāĻĻāĻžāĻšā§°āĻŖāϏāĻš āĻļāĻ•ā§āϤāĻŋ āϏāς⧰āĻ•ā§āώāĻŖā§° āύ⧀āϤāĻŋ āĻŦā§āϝāĻžāĻ–ā§āϝāĻž āϕ⧰āĻžāĨ¤

Ans: The law of conservation of energy states that energy can neither be created nor destroyed. It only changes from one form to another. For example, when a ball falls from a height, its potential energy gradually changes into kinetic energy. At the top, potential energy is maximum and kinetic energy is minimum. As the ball falls, kinetic energy increases and potential energy decreases.


āωāĻ¤ā§āϤ⧰: āĻļāĻ•ā§āϤāĻŋ āϏāς⧰āĻ•ā§āώāĻŖā§° āύ⧀āϤāĻŋ āĻ…āύ⧁āϏ⧰āĻŋ āĻļāĻ•ā§āϤāĻŋ āϏ⧃āĻˇā§āϟāĻŋ āĻŦāĻž āĻ§ā§āĻŦāĻ‚āϏ āϕ⧰āĻŋāĻŦ āĻ¨ā§‹ā§ąāĻžā§°āĻŋāĨ¤ āχ āĻ•ā§‡ā§ąāϞ āĻāϟāĻž ā§°ā§‚āĻĒā§° āĻĒā§°āĻž āφāύ āĻāϟāĻž ā§°ā§‚āĻĒāϞ⧈ āĻĒā§°āĻŋāĻŦā§°ā§āϤāĻŋāϤ āĻšāϝāĻŧāĨ¤ āωāĻĻāĻžāĻšā§°āĻŖāĻ¸ā§āĻŦā§°ā§‚āĻĒ⧇, āĻ“āĻĒā§°ā§° āĻĒā§°āĻž āĻāϟāĻž āĻŦāϞ āĻĒ⧇āϞāĻžāϞ⧇ āϤāĻžā§° āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āϧ⧀āϰ⧇ āϧ⧀āϰ⧇ āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋāϞ⧈ āĻĒā§°āĻŋāĻŦā§°ā§āϤāĻŋāϤ āĻšāϝāĻŧāĨ¤ āĻ“āĻĒā§°āϤ āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āĻ¸ā§°ā§āĻŦāĻžāϧāĻŋāĻ• āφ⧰⧁ āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āĻ¸ā§°ā§āĻŦāύāĻŋāĻŽā§āύ āĻĨāĻžāϕ⧇āĨ¤ āĻŦāϞāĻŸā§‹ āϤāϞāϞ⧈ āύāĻžāĻŽāĻŋ āφāĻšā§‹āρāϤ⧇ āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āĻŦ⧃āĻĻā§āϧāĻŋ āĻĒāĻžāϝāĻŧ āφ⧰⧁ āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āĻ•āĻŽāĻŋ āϝāĻžāϝāĻŧāĨ¤


2. Define kinetic energy and derive its formula. āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋā§° āϏāĻ‚āĻœā§āĻžāĻž āĻĻāĻŋāϝāĻŧāĻž āφ⧰⧁ āχāϝāĻŧāĻžā§° āϏ⧂āĻ¤ā§ā§° āϞāĻŋāĻ–āĻžāĨ¤

Ans): Kinetic energy is the energy possessed by a moving body. It depends on the mass and velocity of the body.


Formula: KE = 1/2mv2


Where: = mass,  = velocity


āωāĻ¤ā§āϤ⧰: āĻ—āϤāĻŋ āĻĨāĻ•āĻž āĻŦāĻ¸ā§āϤ⧁āϤ āĻĨāĻ•āĻž āĻļāĻ•ā§āϤāĻŋāĻ• āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āĻŦā§‹āϞāĻž āĻšāϝāĻŧāĨ¤ āχ āĻŦāĻ¸ā§āϤ⧁⧰ āĻ­ā§° āφ⧰⧁ āĻŦ⧇āĻ—ā§° āĻ“āĻĒā§°āϤ āύāĻŋā§°ā§āĻ­ā§° āϕ⧰⧇āĨ¤


3. What is potential energy ? Write its formula and SI unit. : āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āĻ•āĻŋ ? āχāϝāĻŧāĻžā§° āϏ⧂āĻ¤ā§ā§° āφ⧰⧁ SI āĻāĻ•āĻ• āϞāĻŋāĻ–āĻžāĨ¤

Ans: Potential energy is the energy possessed by a body due to its position or height. āϕ⧋āύ⧋ āĻŦāĻ¸ā§āϤ⧁⧰ āĻ…ā§ąāĻ¸ā§āĻĨāĻžāύ āĻŦāĻž āωāĻšā§āϚāϤāĻžā§° āĻŦāĻžāĻŦ⧇ āϞāĻžāĻ­ āϕ⧰āĻž āĻļāĻ•ā§āϤāĻŋāĻ• āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āĻŦā§‹āϞāĻž āĻšāϝāĻŧāĨ¤


Formula: PE = mgh, SI unit: Joule (J)


4. Define work and mention its SI unit. āĻ•āĻžāĻŽā§° āϏāĻ‚āĻœā§āĻžāĻž āĻĻāĻŋāϝāĻŧāĻž āφ⧰⧁ āχāϝāĻŧāĻžā§° SI āĻāĻ•āĻ• āωāĻ˛ā§āϞ⧇āĻ– āϕ⧰āĻžāĨ¤

Ans: Work is done when a force moves an object through a distance in the direction of the force. SI unit of work is Joule (J).


āωāĻ¤ā§āϤ⧰: āĻŦāϞ⧰ āĻĻāĻŋāĻļāϤ āϕ⧋āύ⧋ āĻŦāĻ¸ā§āϤ⧁ āύāĻŋāĻ°ā§āĻĻāĻŋāĻˇā§āϟ āĻĻā§‚ā§°āĻ¤ā§āĻŦ āĻ—āϤāĻŋ āϕ⧰āĻŋāϞ⧇ āĻ•āĻžāĻŽ āϏāĻŽā§āĻĒāĻ¨ā§āύ āĻšāϝāĻŧāĨ¤ āĻ•āĻžāĻŽā§° SI āĻāĻ•āĻ• āĻšā§ˆāϛ⧇ Joule (J)āĨ¤


5. Differentiate between kinetic energy and potential energy. āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āφ⧰⧁ āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋā§° āĻŽāĻžāϜ⧰ āĻĒāĻžā§°ā§āĻĨāĻ•ā§āϝ āϞāĻŋāĻ–āĻžāĨ¤

Ans: i. Kinetic Energy is energy due to motion. āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āĻšā§ˆāϛ⧇ āĻ—āϤāĻŋā§° āĻŦāĻžāĻŦ⧇ āϞāĻžāĻ­ āϕ⧰āĻž āĻļāĻ•ā§āϤāĻŋāĨ¤


ii. Potential Energy is energy due to position. āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āĻšā§ˆāϛ⧇ āĻ…ā§ąāĻ¸ā§āĻĨāĻžāύ⧰ āĻŦāĻžāĻŦ⧇ āϞāĻžāĻ­ āϕ⧰āĻž āĻļāĻ•ā§āϤāĻŋāĨ¤


iii.  Kinetic Energy depends on velocity. āĻ—āϤāĻŋāĻļāĻ•ā§āϤāĻŋ āĻŦ⧇āĻ—ā§° āĻ“āĻĒā§°āϤ āύāĻŋā§°ā§āĻ­ā§° āϕ⧰⧇āĨ¤

iv. Potential Energy depends on height or position. āĻŦāĻŋāĻ­ā§ą āĻļāĻ•ā§āϤāĻŋ āωāĻšā§āϚāϤāĻž āĻŦāĻž āĻ…ā§ąāĻ¸ā§āĻĨāĻžāύ⧰ āĻ“āĻĒā§°āϤ āύāĻŋā§°ā§āĻ­ā§° āϕ⧰⧇āĨ¤