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9th Class Science Force and laws of motion Question Bank Force And Laws Of Motion IIT JEE Objective Problems

  • question_answer
    A ball of mass 100 g is moving with a velocity of 10 m/s and hits a bat and rebounds with a velocity of 10 m/s. The force of the blow by the bat acts for 0.01 s. The average force exerted on the ball b the bat is

    A)  50 N                     

    B)  100 N

    C)  200 N                   

    D)  zero

    Correct Answer: C

    Solution :

       Given, \[m=100\text{ }g=\frac{100}{1000}=0.1\,kg\] \[u=10\text{ }m/s\] \[v=10\text{ }m/s\]               (\[\because \] the ball is rebouncing) \[F=?\] we know, \[F=ma=m\left( \frac{v-u}{t} \right)\]    \[\left( \because a=\frac{v-u}{t} \right)\] \[\Rightarrow \] \[\left( 0.1\times \frac{-10-10}{0.01} \right)=\frac{0.1\times -20}{0.01}=-200\,N\] (\[\because \] the negative sign indicates the force is in opposite direction) \[\therefore \] \[F=200\text{ }N\]


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