Q123 / 160 · AP EAMCET 2020 (17 Sep Shift 2) · Physics

A body of mass \(10 \mathrm{~kg}\) has constant velocity of \(10 \mathrm{~m} \mathrm{~s}^{-1}\). A constant force is applied for a duration of \(4 \mathrm{~s}\) on the object and gives it a speed of \(2 \mathrm{~m} \mathrm{~s}^{-1}\) in opposite direction. Then, find acceleration produced in it.

  • A
    \(3 \mathrm{~ms}^{-2}\)
  • Correct answer
    B
    \(-3 \mathrm{~ms}^{-2}\)
  • C
    \(0.3 \mathrm{~ms}^{-2}\)
  • D
    \(-0.3 \mathrm{~ms}^{-2}\)

Solution

Mass of body, \(m=10 \mathrm{~kg}\) Velocity, \(v=10 \mathrm{~ms}^{-1}\) \(t=4 \mathrm{~s}\) Final velocity of the body, \(v=-2 \mathrm{~ms}^{-1}\) Since, final velocity of the body decreases on application of constant force, hence acceleration is negative. By first equation of motion, \(\Rightarrow \quad \begin{aligned} & v=u+a t \\ & \quad a=\frac{v-u}{t}=\frac{-2-10}{4}=-\frac{12}{4}=-3 \mathrm{~ms}^{-2} \end{aligned}\)

Hence, the correct answer is option: 'B'.

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