JEE Main & Advanced Physics Gravitation / गुरुत्वाकर्षण Question Bank Self Evaluation Test - Gravitation

  • question_answer
    The ratio of radii of earth to another planet is 21 3 and the ratio of their mean densities is 4/5. If an astronaut can jump to a maximum height of 1.5 m on the earth, with the same effort, the maximum height he can jump on the planet is

    A) 1 m      

    B)        0.8 m

    C) 0.5 m   

    D)        125 m

    Correct Answer: B

    Solution :

    [b] to K.E. of the person = P.E. at the maximum height \[\frac{1}{2}m{{v}^{2}}=m\frac{GM}{{{R}^{2}}}h.\] \[\therefore m\frac{GM}{{{R}^{2}}}.h=mG\frac{M'}{R{{'}^{2}}}h'\] Given \[\rho =\frac{4}{5}p',\frac{R}{R'}=\frac{2}{3}\] \[\therefore mG.\frac{4}{3}\frac{\pi {{R}^{3}}\rho }{{{R}^{2}}}.h=mG.\frac{4}{3}\frac{\pi R{{'}^{3}}\rho '}{R{{'}^{2}}}.h'\] \[\Rightarrow \frac{2}{3}R.\frac{4}{5}\rho '1.5=R'\rho 'h'\therefore h'=0.8m.\]


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