Work, Energy & Power PDF

Work, Energy & Power Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Work ◼ Work is said to be done only when the force applied on body makes the body move (i.e., there is a displacement of the body). Measurement of Work ◼ The amount of work done on a bod...

Work, Energy & Power Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Work ◼ Work is said to be done only when the force applied on body makes the body move (i.e., there is a displacement of the body). Measurement of Work ◼ The amount of work done on a body depends on two factors: ◼ Magnitude of the force applied ◼ Displacement produced by the force Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Moment of Work: ◼ The amount of work done by a force is equal to the product of the force and the displacement of the point of application of the force in the direction of force. ◼ Work = force x displacement of the point of application of force in the direction of force. ◼ W = F x S Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Expression of Work (W = F S Cosθ ◼ By finding the component of displacement along the force: A Constant force F acts on a body along AB and displaces the body on an inclined surface from A to C. The displacement of the body from the point of application of force is AC = S. W = F x S cosθ Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Expression of Work (W = F S Cosθ ◼ By finding the component of force along the displacement: If PA represents the magnitude and direction of force F acting on the body, then the component of force F in the direction of displacement (i.e., along AC) is NA. W = F cosθ x S Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Special Cases: ◼ If the displacement is in the direction of force, i.e., 0=0°, then cos 0° = 1. Examples: ◼ 1. In free fall of a body of mass m under gravity through a height h from A to B, the force of gravity F(= mg) is in the direction of displacement S (= h) and the work done by the force of gravity is W = FS = mgh. ◼ W=FxS Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Special Cases: ◼ When the displacement is normal to the direction of force, i.e., 0 = 90°, then cos 90° = 0. ◼ Examples: ◼ When a coolie walks on a horizontal ground while carrying a load on his head, no work is done against the force of gravity because the displacement of load is normal to the direction of force of gravity which is vertically downwards. ◼ W=0 Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Special Cases: ◼ If the displacement is in a direction opposite to the force, i.e., 0 = 180°, then cos 180 degrees = - 1. ◼ Examples: ◼ When a body moves on a surface, the force of friction between the body and the surface is in a direction opposite to the motion of the body (i.e. 0 = 180°). Thus, the work done by the force of friction is negative. ◼ W=-1 Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu  Conditions for the work done by a force to be zero: ◼ when there is no displacement (i.e., S=0) , and ◼ when the displacement is normal to the direction of force (i.e., θ = 90 degrees). Work Done by the Force of Gravity : ◼ Work done by the force of gravity is same whether the body comes down from a certain height using stairs or slope or a lift (or elevator). ◼ If a body of mass m goes up through a vertical height h either directly or through stairs or slope or lift, the work W = - mgh is done by the force of gravity on the body. Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Units of Work : ◼ SI Unit of work is Joule. ◼ Since, work = force x displacement ∴ 1 Joule = 1 newton x 1 metre ◼ 1 joule of work is said to be done when a force of 1 newton displaces a body through a distance of 1 metre in its own direction. ◼ CGS Unit of work is erg. Where, 1 erg = 1 dyne x 1 cm ◼ 1 erg of work is said to be done when a force of 1 dyne displaces a body through a distance of 1 cm in its own direction. Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Relationship between joule and erg: 1 Joule = 1 N x 1 m But, 1 N = 105 dyne and 1 m = 102 cm ∴ 1 Joule = 105 dyne x 102 cm = 107 dyne x cm = 107 erg 1 Joule = 107 erg Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu  Power The rate of doing work is called POWER! Power is a scalar quantity. SI Unit Of POWER = WATT If 1 joule of work is done in 1 sec , the power spent is 1 watt. Bigger unit : Kilowatt, Mega Watt Smaller unit : milliwatt, microwatt CGS Unit = erg/second Horse Power: used in Mechanical engineering. 1 HP = 746 Watt Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu  MECHANICAL ENERGY AND ITS DIFFERENT FORMS The energy possessed by a body due to its state of rest or of motion, is called mechanical energy. It is in two forms: (1) potential energy, and (2) kinetic energy Energy is also a scalar quantity. SI Unit = Joule CGS Unit = erg Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu  Potential Energy: The energy possessed by a body at rest due to its position or size and shape is called potential energy. It is usually denoted by the symbol U. Forms of Potential Energy: In mechanics, potential energy is mainly of two kinds : (1) Gravitational potential energy due to its changed position, and (2) Elastic potential energy due to its changed size and shape Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu (1) Gravitational Potential Energy: The potential energy possessed by a body due to the force of attraction of Earth on it, is called its gravitational potential energy. (2) Elastic Potential Energy: The potential energy possessed by a body in the deformed state due to change in its size and shape is called elastic potential energy. Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu  GRAVITATIONAL POTENTIAL ENERGY AT A HEIGHT (U = mgh) The gravitational potential energy of a body at a height above the ground is measured by the amount of work done in lifting it up from the ground to that height against the force of gravity (assuming that its gravitational potential energy on the ground is zero). It is usually denoted by the symbol U. Gravitational potential energy U = mgh Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu  Kinetic Energy (K): The energy possessed by a body due to its state of motion is called its kinetic energy. It is usually denoted by the symbol K. Relationship between Kinetic Energy & Momentum Kinetic energy K = ½ mv² (i) Momentum p = mv (ii) P =√2mK or K = p²/2m Work Energy Theorem: The increase in kinetic energy of a moving body is equal to the work done by a force acting in the direction of the moving body. W = ½ mv² - ½ mu² Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu  Forms of Kinetic Energy: (1) Translational Kinetic Energy: The motion of a body in a straight line path is called translational motion. Ex- a freely falling body (2) Rotational Kinetic Energy: If a body rotates about an axis, the motion is called rotational motion. Ex- a spinning top (3) Vibrational Kinetic Energy: If a body moves to and fro about its mean position, the motion is called vibrational motion. Ex- a vibrating tuning fork Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu  Different Forms of Energy : 1) Electrical Energy: When two dry bodies are rubbed together, they get charged due to the movement of free electrons from one body to the other body, so they possess electrical energy. 2) Chemical Energy: The energy possessed by the fossil fuels such as coal, petroleum and natural gas is called Chemical Energy. 3) Heat Energy: The energy released on burning coal, oil, wood or gas is called heat energy. Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu  Different Forms of Energy: 4) Nuclear Energy: The energy released due to loss in mass during the processes of nuclear fission and fusion, is called nuclear (or atomic) energy. 5) Light Energy: It is a form of energy in the presence of which other objects are seen. 6) Sound Energy: A vibrating body possesses sound energy. Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu  Energy: The capacity to do work. It is a scalar quantity. ◼ SI Unit of Energy = JOULES (J) ◼ CGS Unit = Erg ◼ 4.18 J = 1 calorie ◼ 1 Watt Hour= 1 watt * 1 hour ◼ = 3600 J ◼ 1 kilowatt Hour = 1 Kw * 1 Hour ◼ = 3600 * 1000 J Electron Volt = energy gained by an electron when accelerated by pd of 1 volt. 1eV = 1.6 * 10(power -19)J Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu ENERGY IS CONSERVED The law of conservation of energy states: Energy cannot be created nor be destroyed, it can only be transformed! Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu Law of conservation of energy in a simple pendulum Click here to buy Latest ICSE Class 10 Books-https://amzn.to/3xib8Bu