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

  • question_answer
    A ball of mass m is thrown vertically up. Another hall of mass 2 m is thrown at an angle 6 with the vertical. Both of them stay in air for the same period of time. What is the ratio of the height attained by the two balls.

    Answer:

                    For the ball thrown vertically upwards, the time taken by the ball to come back is,  \[{{T}_{1}}=2{{\mu }_{1}}/g\]. For the ball projected at an angle 9 with their vertical, the time of flight is,       \[{{T}_{2}}=2{{\mu }_{2}}\cos \theta /g\] Since time for both the balls is same, so \[\frac{2{{u}_{1}}}{g}=\frac{2{{u}_{2}}\cos \theta }{g}\]or \[{{u}_{1}}={{u}_{2}}\cos \theta \]. Now, \[{{h}_{1}}=\frac{u_{1}^{2}}{2g}\]and \[{{h}_{2}}=\frac{u_{2}^{2}}{2g}{{\cos }^{2}}\theta \]; Hence, \[\frac{{{h}_{1}}}{{{h}_{2}}}=\frac{u_{1}^{2}}{u_{2}^{2}{{\cos }^{2}}\theta }=\frac{u_{2}^{2}{{\cos }^{2}}\theta }{u_{2}^{2}{{\cos }^{2}}\theta }=1\]


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