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Published byVictor Peters Modified over 6 years ago

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"The ability of a body to perform work is, Energy". The unit of energy is, joule (J). Larger unit of energy is kilo joule (kJ). 1 kJ = 1000 J. There are numerous types of energy such as: Heat Energy Light Energy Chemical Energy Electrical Energy Kinetic Energy Potential Energy etc. Energy Work and Energy

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Energy posses by a body by virtue of its motion is ‘Kinetic Energy’. Kinetic energy depends upon the mass and velocity of body. If velocity is zero than K.E. of body will also be zero. Kinetic Energy Work and Energy

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Consider a body of mass "m" starts moving from rest. After a time interval "t" its velocity becomes V. If initial velocity of the body is V i = 0,final velocity V f = V and the displacement of body is "d". Kinetic Energy Work and Energy

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Then,using equation of motion 2aS = V f 2 – V i 2 Putting the above mentioned values 2ad = V 2 – 0 a = V 2 /2d Now force is given by F = ma Putting the value of acceleration F = m(V 2 /2d) As we know that Work done = Fd Kinetic Energy Work and Energy

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Putting the value of F Work done = (mV 2 /2d)(d) = mV 2 /2 OR Work done = ½ mV 2 Since the work done in motion is called "Kinetic Energy “i.e. “ K.E. = Work done OR K.E. =1/2mV 2. Kinetic Energy Work and Energy

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Consider a body of mass "m" placed at a height of "h" from the surface of earth. Force = Weight = W and displacement (d) = h Work done = Fd = Wh [but W = mg] work done = mgh We know that the work done in lifting the body is stored in the body in the form of Potential Energy. Thus, P.E. = mgh Potential Energy Work and Energy

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Kinetic and Potential Energy

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An object of mass 15 kg is moving with a uniform velocity of 4 m s –1. What is the kinetic energy possessed by the object? Work and Energy Example

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Mass of the object, m = 15 kg, velocity of the object, v = 4 m s –1. K.E. =½ mv 2 =½× 15 kg × 4 m s –1 × 4 m s –1 = 120 J The kinetic energy of the object is 120 J. Work and Energy Solution

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Work and Energy Find the energy possessed by an object of mass 10 kg when it is at a height of 6 m above the ground. Given, g = 9.8 m s –2. Example

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Mass of the object, m = 10 kg, Displacement (height), h = 6 m, and Acceleration due to gravity, g = 9.8 m s –2. Potential energy = mgh = 10 kg × 9.8 m s –2 × 6 m = 588 J. The potential energy is 588 J. Work and Energy Solution

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