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

  • question_answer
    A hammer weighing 2.5 kg moving with a speed of \[1\text{ }m\text{ }{{s}^{-1}}\] strikes the head of the nail driving it 10 cm into the wall. The acceleration during impact and the impulse imparted to wall will be respectively

    A) \[-5m\text{ }{{s}^{-2}},\text{ }2.5\text{ }N\text{ }s\]

    B) \[-\text{ }10\text{ }m\text{ }{{s}^{-2}},\text{ }5\text{ }N\text{ }s\]

    C) \[-\text{ }7.5\text{ }m\text{ }{{s}^{-2}},\text{ }3.5\text{ }N\text{ }s\]

    D)  \[-6m\text{ }{{s}^{-2}},\text{ }4\text{ }N\text{ }s\]

    Correct Answer: A

    Solution :

    Here, \[m\text{ }=\text{ }2.5\text{ }kg,\text{ }v\text{ }=\text{ }1\text{ }m\text{ }{{s}^{-1}},\] \[s\text{ }=\text{ }10\text{ }cm\text{ }=\text{ }0.1\text{ }m\] Using, \[{{v}^{2}}={{u}^{2}}+2as\] or \[{{1}^{2}}=0+2(-a)\times 0.1\] or \[a=\frac{-10}{2}=-5m{{s}^{-2}}\]             (negative sign indicates deceleration) We know, Impulse, \[I={{F}_{avg}}\times t=\]Final linear momentum- Initial linear momentum \[=m(v-u)=m(v-0)=2.5\times 1=2.5Ns\]


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