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What is potential energy ? Explain gravitational potential energy . |
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Answer» Solution :Potential energy is the stored energy by virtue of the position or CONFIGURATION of the body .If configuration of the system changes , then its potential energy changes . Gravitational potential energy : MULTIPLICATION of weightof the body and its height from the surface of earth is called the gravitational potential energy relative to the surface of earth . Suppose a ball of mass is lie down of earth surface the gravitational force acting on it is mg . If this ball lifted upto height h from the surface ofearth , then externalforce of mg exerted on it in upward direction . Work done by external force `W = Fd COS theta ` but F = mg, d = h and `theta =0^(0)`(External force and displacement are in upward direction hence `theta = 0^(@)`) ` :. W = mgh cos 0^(@)` ` :. W = mgh ` This type of amount of work is stored as gravitational potential energy . Work doneby gravitational force `W = - mgh` ` :. ` Magnitude of gravitational potential energy is equal to the negative value of work done by gravitational force . ` :. V(h) = 0 mgh` where V(h) = gravitational potential energy ` :, (dV(h))/(dh) = - mg ` `= - F ` where F is the gravitational force and it is in downward direction and so it is negative. When a ball fall freely then its speed increases . Its speed is obtained when it touches the earth by equation of MOTION , `v^(2) - u^(2) = 2gh ` For free fall , u = 0 ` : v^(2) =2gh` MULTIPLYING `m/2` on both sides . ` 1/2 mv^(2) = mgh` It indicates that gravitational potential energy of free fall body converted into kinetic energy . Dimensional formula of potential energy `[M^(1)L^(2)T^(-2)]` and its SI unit is Joule . |
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