Question

Figure gives the acceleration of a $2.0 \,kg$ body as it moves from rest along $x$ axis while a variable force acts on it from $x=0\,m$ to $x=9\,m$ . The work done by the force on the body when it reaches (i) $x=4\,m$ and (ii) $x=7\,m$ shall be as given below

• A. 21 J and 33 J respectively
• B. 21 J and 15 J respectively
• C. 42 J and 60 J respectively
• D. 42 J and 30 J respectively

Answer 1

Answer: (D)

42 J and 30 J respectively

Answer 2

From figure Work done $(W) = \max$
$W_{4}=2\left[ \frac{1}{2}\times 1\times 6+3\times 6 \right] = 42 \,J$
$W_{7}=2\,[21+3-3-1\times 6]$
$=30\,J$