11th Class Physics Motion in a Straight Line / सरल रेखा में गति Question Bank 11th CBSE Physics One Dimensional Motion

  • question_answer
         At which point of projectile motion (i) potential energy is maximum (ii) kinetic energy is maximum (iii) total mechanical energy is maximum.

    Answer:

                    In case of a projectile, the potential energy is maximum at the highest point, given by \[\therefore \]  \[{{\left( P.E. \right)}_{H}}=mgH=mg\frac{{{u}^{2}}{{\sin }^{2}}\theta }{2g}=\frac{1}{2}m{{u}^{2}}{{\sin }^{2}}\theta \] Kinetic energy of projectile will be minimum (but not zero) at the highest point, because only vertical component velocity is zero there. Therefore \[{{\left( K.E. \right)}_{H}}=\frac{1}{2}mu_{H}^{2}=\frac{1}{2}m{{u}^{2}}{{\cos }^{2}}\theta \] \[\therefore \]  \[{{\left( P.E. \right)}_{H}}+{{\left( K.E. \right)}_{H}}=\frac{1}{2}m{{u}^{2}}\left( {{\sin }^{2}}\theta +{{\cos }^{2}}\theta  \right)=\frac{1}{2}m{{u}^{2}}\] which is the total mechanical energy of projectile at the point of projection. So in projectile motion, total mechanical energy is conserved i.e. same at all locations of its motion. K.E. of projectile is maximum at place of projection.


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