9th Class Science Force and laws of motion Question Bank Force and Laws of Motion

  • question_answer
    A sphere of mass m moving with a constant velocity u hits another stationary sphere of same mass. If e is the coefficient of restitution, then ratio of velocities of the two spheres after collision will be

    A)  \[\frac{1-e}{1+e}\]          

    B)         \[\frac{1+e}{1-e}\]

    C)  \[\frac{e-1}{1-e}\]         

    D)         \[\frac{e-1}{1+e}\]

    Correct Answer: A

    Solution :

                \[e=\frac{{{v}_{2}}-{{v}_{1}}}{{{u}_{1}}-{{u}_{2}}}=\frac{{{v}_{2}}-{{v}_{1}}}{u-0}\] \[\Rightarrow \]   \[{{v}_{2}}-{{v}_{1}}=e\,\,u\] By conservation of momentum,             \[mu=m{{v}_{1}}+m{{v}_{2}}\] \[\Rightarrow \]   \[{{v}_{1}}+{{v}_{2}}=u\] On solving,\[\frac{{{v}_{1}}}{{{v}_{2}}}=\frac{1-e}{1+e}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner