11th Class Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति Question Bank 11th CBSE Physics Work, Energy, Power & Collision

  • question_answer
    A light body and a heavy body have same linear momentum. Which one has greater K.E.?

    Answer:

                    Here \[{{\text{p}}_{\text{1}}}={{\text{p}}_{\text{2}}}\], i.e., \[{{\text{m}}_{\text{1}}}{{\upsilon }_{\text{1}}}={{\text{m}}_{\text{2}}}{{\upsilon }_{\text{2}}}\]                      \[\therefore \]   \[\frac{{{\upsilon }_{1}}}{{{\upsilon }_{2}}}=\frac{{{m}_{1}}}{{{m}_{2}}}\]                                    ...(i) As \[{{\text{E}}_{\text{2}}}=\frac{1}{2}{{\text{m}}_{\text{2}}}\upsilon _{2}^{2}\]                      and                 \[{{\text{E}}_{1}}=\frac{1}{2}{{\text{m}}_{1}}\upsilon _{1}^{2}\]               \[\therefore \]            \[\frac{{{E}_{2}}}{{{E}_{1}}}=\frac{\frac{1}{2}{{m}_{2}}\upsilon _{2}^{2}}{\frac{1}{2}{{m}_{1}}\upsilon _{1}^{2}}=\frac{{{m}_{2}}}{{{m}_{1}}}{{\left( \frac{{{\upsilon }_{2}}}{{{\upsilon }_{1}}} \right)}^{2}}\] using (i), \[\frac{{{E}_{2}}}{{{E}_{1}}}=\frac{{{m}_{2}}}{{{m}_{1}}}.{{\left( \frac{{{m}_{1}}}{{{m}_{2}}} \right)}^{2}}=\frac{{{m}_{1}}}{{{m}_{2}}}\] If \[{{\text{m}}_{\text{1}}}<{{\text{m}}_{\text{2}}},{{\text{E}}_{\text{1}}}<\text{ }{{\text{E}}_{\text{1}}}\] or \[{{\text{E}}_{\text{1}}}>\text{ }{{\text{E}}_{\text{2}}}\]i.e. lighter body has more K.E.


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